[HereBeBeasties]

For Windows, Snapchat have a standalone virtual cam called Snapcamera https://snapcamera.snapchat.com/

There are green screen plugins for that. You could chain Snapcamera's virtual cam output into OBS and use OBS 's chromakey filter to underlay whatever other content you like. Y I u can then output OBS to another virtual cam output for use in Zoom or wherever else via the Virtualcam plugin for OBS.

It'd be really nice if someone would make a nice OpenCV virtualcam output so one could drive all this from a (relatively) simple Python script.

[soylentcola]

Oh hey, this worked fairly well. I used one of the Snap fake-greenscreen filters and fed it to OBS as you suggested. It really does highlight the limitations of fake-chromakey (edges are fuzzy/flickery) but that's to be expected without a real, properly lit backdrop.

I won't be using this in any work meetings but it could be fun for calls with friends.