My video conference rig is a Micro Studio Camera 4K, Video Assist 4k, and Arduino shield all going into a Decklink card on an Ubuntu desktop machine. The Studio Camera, Video Assist and Arduino shield all get pretty hot, so I don't run them continuously. The Video Assist does weird things when it's hot like having the audio meters stop working, even though it's still transmitting audio to the SDI output just fine.
That said, the Decklink has been rock-solid in the 5+ years I've owned it and we had a VideoHub at a past workplace that worked great. I actually recommend all the Blackmagic stuff I've worked with, but have seen heat consistently been an issue.
> Apple announced external GPU support at last year’s WWDC, finally rolling out support for the feature back in March.
I'm surprised. I guess I'd always assumed that they'd already implemented that for the trash-can Mac Pro. IIRC, one of the selling points was thunderbolt was so fast that card slots were obsolete, so if you needed to upgrade the GPU you could just use thunderbolt.