One issue I did run into was getting a decent HDMI -> USB capture device that works with Linux. My first choice was a high end (~£200) ClonerAlliance Flint 4KP [1] which worked fine for Hangouts, but had issues with Zoom and actually seemed to get worse as time went on and it eventually became a bit of a joke as I tried to join calls and had to restart my camera, unplug cables, etc. just to get video. Eventually, I swapped it out for a cheap £15 no-name brand from Amazon and have had literally 0 issues since [2].
The biggest drawback to this sort of setup is that if you're using a camera you already own, it can be a pain to switch between using it as a camera and using it as a web cam, so I've essentially got an expensive camera that I don't get to use as a camera very often. The advantage of course is that even on a dark, rainy evening with nothing more than a small lamp hidden behind my monitor, the image still comes out looking great [3].
[1] https://www.amazon.co.uk/gp/product/B07YY52YP6/