Stream your Android camera over RTSP directly to OBS with TONE!
This is horribly b0rked at the moment, but hey, you can use it if you feel adventurous! It's a minimal streaming app that works as an RTSP server - once you press Stream, it'll open a server (on port 8086 by default, you can change this in settings) to which you can connect with OBS (Media Source plugin - use rtsp://your_device_ip_addr:port
as the input) or mpv (rtsp://your_device_ip_addr:port --rtsp-transport=udp
).
But then, it's horribly buggy, so you might want to find something else for now.