You can probably use an Elgato Facecam (Mk.2), configure it in a Windows VM and then save the settings directly on the device to use it under Linux.

XMPP only does it with certain client extensions. And Matrix only does it when the rooms are set up this way. SimpleX does what you want, but is kind of unintuitive for the average user.
I say go with Signal, it does what you want and is idiot-proof.