Great to see someone playing with this. Check out this github request here as it should be possible and it may be what you have already have working, to use a widget to side load a webRTC connection to play a RTSP stream.
Simple RTSP support via Video Widget · Issue #10591 · openhab/openhab-addons (github.com)
There are webrtc javascript players for both RTSP and also HLS streams. Should be simple if you know how to side load the javascript players that people embed into websites.