No? Most were released on 7/7? Only the 3950X and some OEM CPUs came later.

Do you want to tell me that press release from June 16 is not an announcement and that "Expected Availability: July 7, 2020" actually means "release in september"?
https://www.amd.com/en/press-releases/2020-06-16-amd-offers-enthusiasts-more-choice-ever-new-ryzen-3000xt-processors

4.1 is barely an overclock considering the 4770K starts with 3.9. I'm surprised you couldn't even get 4.2 stable, the average OC is 4.5. No offense, but that doesn't exactly inspire confidence so unless you're willing to invest enough time to learn how to do it properly I wouldn't go for overclocking on the new build.
You're already using GPU encoding so CPU load from streaming obviously isn't the problem. GPU encoding doesn't cause any GPU load either though.

Fps in TF2 will always be inconsistent. A new pc will not fix that. There's also a slight problem: If you want those minimum 120 fps to become 240 you'd need a CPU that's twice as fast and there simply is none.

First lets clarify a few things: Did you mean AMD will be releasing CPUs? Because there will be no GPUs. Also I'm not sure how you got the idea that Intel would be releasing new CPUs from " the 3600XT will be released in 5 days". Intel 10th Gen/Comet Lake has already been released on April 30th. Intel made a big show out of releasing before AMD. Turns out they don't actually have enough CPUs so it's essentially a paper launch and availability is dogshit.
All of AMD's 6 cores had SMT since 2017 (and their implementation is a bit better than Intel's anyway, even if it doesn't have a fancy marketing name) so i5s getting that now so they don't get shit on in multithreaded workloads for the third year in a row only closes that gap. Still not enough to win unless they already got such a significant advantage in single threaded/clockrate that it's enough to overcome their disadvantage in SMT.

Like I said, release on 7/7 so they should be available around the same time.
I don't really have an accurate read on what you'd need these days to get 240 fps (and it also depends on the settings) but I highly doubt it'll be 5 GHz. So I'd just get something that's not crippled by a 2.x GHz baseclock and with 4.5-ish or more turbo and hope for the best. Not exactly the most professional approach but it should do. If you tell me what clockrate your 4770K is running at and how many fps you're getting right now (unless you only need more when streaming, then anything not slower than a 4770K with more cores will do) I can make a better estimate of what you actually need. My guess is you wouldn't need to overclock.
Turbo/Boost clocks and overclocking aren't mutually exclusive. No one overclocks by locking the clockrate anymore. Idle, normal and turbo states still work and are switched to when appropriate, regardless of what multipliers are set as maximum.
The performance gain is still roughly linear. The more important question is do you need it? If you can get let's say 250 fps at stock it doesn't matter if overclocking would get you an extra 10 or an extra 100 fps. You don't have to spend any money and time on it if you don't need it.

Yes, streaming affects the build significantly. Either you want a lot of cores or GPU encoding. The number of monitors don't matter unless you want more than 4 (nVidia) or 6 (AMD).
I haven't done any testing with DDR4 but I've seen >10% in my testing. Super expensive RAM still doesn't make any sense but going from the cheapest RAM to something fairly good is about the same as overclocking from 4.5 to 5.0 GHz so I definitely wouldn't cheap out on it. 3200 MHz CL16 minimum, 3600 MHz CL16 if the price is ok though CL17 or 18 is still better than 3200/16.

GPU encoding would be better, both performance wise and in terms of quality should you get an nVidia card, unless you bend over backwards to cram an unreasonable number of CPU cores into your budget. Since you want a new GPU anyway I would recommend going with that. In that case you could cheap out and go with a quad core but AMD doesn't really do those anymore and buying a 150$ mobo for a 150$ quad core Intel CPU just to be able to use RAM faster than 2666 MHz feels really weird. Also for when you do do some video editing and maybe VR stuff that taxes the CPU a bit more it's nice having 6 cores.
Realistically with your budget you can easily afford a 3600X(T) and a 2060 Super or even 2070 Super, maybe a new NVMe SSD if you want it. GPU wise that might actually be overkill.
https://pcpartpicker.com/list/rFffTC
That's just a rough sketch, but you get the idea.

3 steps now:
1. Tell me about the clockrate and fps so we can figure out how much single threaded performance you actually need.
2. Make a decision regarding GPU vs CPU encoding. (dislike of nVidia is a perfectly valid rerason for going with and AMD GPU which means a bit of a quality tradeoff when using GPU encoding or even using CPU encoding)
3. Wait for the new CPUs.

#3638
I know your old PC got RAM. DDR3 still isn't going to fit into DDR4 slots, regardless of the capacity.

1000$ still gets you a good PC.

You want an easy answer when there is no easy answer. For example an i5-10500 and R5 3600X cost about the same. The 10500 is going to be a bit faster in most single threaded workloads (though slightly slower in some, there are always exceptions) but slower in multi-threaded if all other things are equal. The problem is they won't be. It's not soldered and the stock cooler isn't anything to write home about so temperatures and therefore clockrates aren't going to be great unless you buy an aftermarket cooler. However if you do that (and even if you don't because the AMD stock cooler is at least ok) you could also overclock the 3600X. The Intel motherboards are also slightly more expensive, unless you want one that actually supports RAM faster than 2666 MHz (all AMD boards do), then it's going to be a lot more expensive. TF2 likes fast RAM. So which CPU ends up actually being faster depends on how much you spend on everything else.
There is no general rule that every Intel CPU will have better single threaded performance than any AMD CPU.
Comparing CPUs with the same price doesn't work because Intel lets you pay more for everything else.
Comparing setups with the same price doesn't work because then there's still overclocking which depends on the time you invest and luck of the draw. You also need to first choose what you can even afford. What cooler? What RAM speed? And so on. Then there's the little problem that the 3600XT will be released in 5 days. B550 mobos will also offer PCIe 4.0, that's another few fps in games that depend more on the GPU.

I can tell you that if you spend 530$ on an i9-10900K, 200$ on RAM, 200$ on a Z490, 70-100$ on a cooler and then overclock it it's going to be faster single threaded than anything AMD got to offer, but beyond that everything depends on your budget.
It's all nice and good that an overclocked i5-10600K(F) will definitely beat a 3600X, overclocked or not (at least single threaded), and they've nominally got almost the same MSRP (+13$ for the K, -12$ for the KF without iGPU), but ~60$ more for the CPU (because actual retail prices are 220$ vs 280$), ~50$ more for a mobo that actually allows overclocking and another 40-70$ for a cooler because the K(F) doesn't come with one and you actually want to get an OC, not just barely run it at stock without overheating, makes that all a moot point.

Picking a brand and then choosing what you can afford is stupid.
Figure out how much performance you want/need, whether or not you want to overclock and then pick a CPU that fits the bill, regardless of brand and name.
Or pick a budget, do the rest of the build and then if you also want a GPU see which combinations of CPU, RAM, mobo, cooler and GPU you can still afford.

You'd also need new RAM.
If you want a new case as well that means you can only keep the SSD/HDD, GPU and maybe the PSU. Though at that point you might as well leave that in so you friend doesn't have to rebuild it, just add his own GPU and SSD/HDD. So a new build makes sense, but I'd still keep at least the GPU, HDD unless you have a good reason not to. New SSD might make sense though.

Are the low fps a new problem or just in general and you only now get around to doing something about it?

For CPUs it's about the specific models. If across the whole lineup you'd always pick the same brand the market shares wouldn't be what they are.

Budget?

Around 45-50£:
Cryorig H5 Universal/Ultimate
be quiet! Shadow Rock 3
Alpenföhn Brocken 3
Thermalright Macho Rev. C

Around 60£:
be quiet! Dark Rock 4
Noctua NH-U12S SE-AM4
Phanteks PH-TC14PE if you can get one. A bit louder due to being a dual tower but obviously a bit cooler as well.
Same if you can find an NH-D14. For both you'll have to get a free AM4 mounting kit from the manufacturer though.

Well by the time you buy Matisse Refresh (3600XT) will be a thing. Some general advice:
Either commit to spending a lot of money on overclocking or don't. You'll always be held back by the weakest link.
The 212 Evo is a budget cooler, but it isn't particularly cheap in Australia so it makes no sense to buy it, especially if you're spending 300$ on a mobo.
Though I wouldn't recommend spending that much money on an X570 without a good reason. B450 is good enough and with B550 you wouldn't even have to worry about updating the BIOS for a 3600XT so that'd be both easier and cheaper.
Don't cheap out on the RAM, you can afford better timings. Check the mobo QVL just in case. Nothing worse than RAM that won't work at the advertised frequency with your mobo.
GPU depends on the settings, you might not need a 2070 Super.

https://tpucdn.com/review/nvidia-geforce-rtx-2060-super/images/rainbow-six-siege-1920-1080.png

A 2060 Super is much close to a 2070 than to a 2060. The performance difference is a lot less than the almost 1/3 of the price you save compared to a 2070 Super (and like I said you might not even need a 2060 Super).
That said if you can find a cheaper 2070 Super (e.g. one is on sale for 750$ right now) it's worth considering because it is a significant step up from the 2060 Super/2070.

If your definition of "most" excludes all CPUs from 2017 onward and all before 2015 as well, then yes, it's compatible with most.
LGA1151 and LGA1151-2 are not compatible so you're looking for 6th (6000) and 7th gen (7000) (if you updated the BIOS). No other CPUs will work.

Matisse Refresh (Zen2 CPUs) supposedly 7/7, nVidia GPUs starting in September (whole lineup will need a while). AMD GPUs and Zen3 most likely Q4. Definitely wait at least a month.

Apart from streaming you're just GPU limited. At least I'm fairly sure that risk of rain and valorant aren't CPU limited by a 6700 on lowest settings unless you want >300 fps.

So you absolutely need a new GPU, a new PSU and should probably get a new case as well.
The rest depends on how you want to handle streaming. If you want to stick with CPU encoding I wouldn't stop at 6 cores but you can already barely afford 6 with your budget. Although it is debatable whether you really need an RTX 2060 or could make do with something cheaper. Sure, you need something faster than a 360, but do you really need something 4.5 times as fast?
The other option would be to use GPU encoding, keep everything but the GPU, PSU (you'll need an adapter cable because Dell) and case and be done with it.
https://pcpartpicker.com/list/jn2hwh
Switched to a PSU that's in stock, but honestly, something cheaper would be enough for that 350W build.

#3622
What #3623 said, but he forgot the most important question: Why are you upgrading? What are you trying to achieve?
That's not quite the same as what you're going to use it for, it's about what you want to improve compared to your current pc. That'll decide which parts you need to replace and how much faster the new ones need to be.

Yes.

1st gen would work too. Either way AMD will send you one + return label for free if you can provide proof of purchase for CPU and mobo.

No, Intel uses different sockets. Also "i5" tells me nothing, Intel changes sockets every two years and i5s have existed for well over a decade.

Yeah, unless you need more than 4 PCIe slots µATX will make no difference.

Out of the box and not even CPU-less update means we're done to less than a handful of B450 boards in your price range but they've all got worse VRMs. 90% sure an ASRock B450M Pro4-F would work out of the box and the VRMs aren't that much worse than the Tomahawk's but other than that the stock situation according to pcpartpicker Canada is looking quite dire.
With your budget you could just say fuck it and get an Asus PRIME X570-P or TUF GAMING X570-PLUS (slightly better VRMs)
https://ca.pcpartpicker.com/product/McfFf7/asus-prime-x570-p-atx-am4-motherboard-prime-x570-p
https://ca.pcpartpicker.com/product/whMTwP/asus-tuf-gaming-x570-plus-atx-am4-motherboard-tuf-gaming-x570-plus
though both are massively overkill for just a 3600.

#3615
Contacted me on steam, I assume it's taken care of.

#3616
Are you looking for similar price, similar VRM quality or similar features? You can probably choose at most two out of three.
Does full ATX matter or is µATX fine?
Does it have to work with Ryzen 3000 out of the box or at least allow for CPU-less BIOS updates or are you willing to suffer through the whole ordeal of requesting and using the AMD update/boot kit?
Does it have to be in stock at newegg?

Germans stop running this league for a few days and this is the result.