Unable to play any rtsp Streams - in XUbuntu and Debian
https://forum.videolan.org/viewtopic.php?f=13&t=158071&p=520527 says:
Please note that Debian VLC builds do not support RTSP by Debian policy decision. Use the Flatpak if you need RTSP.
Maybe "use the Flatpak" or "Snap, but not .deb's" helps.