So I’ve seen people saying they can use OBS Virtual cam in Jitsi, however, I am not able to. I have the flatpak install on Ubuntu 20.10, with the v4l2loopback and v4l2sink OBS Virtual cam setup. Virtual cam works in Discord and other video call applications, and sometimes in Firefox (though that is a bit more finicky official site).
IIRC chrome can see the virtual microphone if it has a device name. Check this post