Most of these are just an EPYC server platform, some cursed risers and multiple PSUs (though cryptominer server PSU adapters are probably better). See https://nonint.com/2022/05/30/my-deep-learning-rig/ and https://www.mov-axbx.com/wopr/wopr_concept.html.

You might find the journey of Tinycorp's Tinybox interesting, it's a machine with 6 to 8 4090 GPUs and you should be able to track down a lot of their hardware choices including pictures on their Twitter and other info on George his livestreams.

EPYC + Supermicro + C-Payne retimers/cabling. 208-240V power typically mandatory for the most affordable power supplies (chain a server/crypto PSU for the GPUs from ParallelMiner to an ATX PSU for general use).

Beyond that, not much else.

Basically this but with an extra card on the x8 slot for connecting my monitors: https://www.youtube.com/watch?v=C548PLVwjHA

There's a bunch of similar setups and there are a couple of dozen people that have done something similar on /r/localllama.

I'd like to know too