FWIW/out of curiosity, I just tried poking the emulator that comes with Android Studio, and found an option (under "advanced settings") to route the emulated fr

FWIW/out of curiosity, I just tried poking the emulator that comes with Android Studio, and found an option (under "advanced settings") to route the emulated front or back camera to "Webcam0". This is out of the box on Debian. While definitely a heavyweight approach (yay, installing all of Android Studio - but you also install an update tool), I can confirm it works. (And you can fish out and save the qemu invocation from `ps axfww`, then launch it directly without needing to start anything else, although I think the idiomatic approach is using the `emulator` command.)