I see / saw the problem with every manjaro install in my household. Therefore I used another notebook. 
However the problem is fixed by installing:
https://archlinux.org/packages/extra/x86_64/aribb24/
I found the solution in the vlc arch wiki:
https://wiki.archlinux.org/title/VLC_media_player?msclkid=2a3795f6a62a11ec9027cdbcfddb22e0#RTSP_stream_does_not_load
Now it works, I can watch tv. Thx!