Error while saving Live TV configuration

[TheHellSite]

Hello all,

saving any type of Live TV configuration gives me an error as shown below.

Code:

Server: jellyfin
Version: 10.8.13
OS: Linux
Architecture: X64

1. Go to: Jellyfin --> Live-TV
   
2. Add Tuner --> M3U Tuner
   
3. Provide the path to the m3u file --> press Ok
   
4. Hit Save.
   
5. "Alert: There was an error saving the TV provider. Please ensure it is accessible and try again."
   

Everytime I hit Save the below error appears in the logfile.

Code:

[2024-02-12 15:55:46.503 +01:00] [INF] [35] Jellyfin.Api.Auth.CustomAuthenticationHandler: AuthenticationScheme: "CustomAuthentication" was forbidden.

It is not a permission issue between the jellyfin user and the m3u file, since it is stored in the same directory as the other media files.
Not even with the user jellyfin as the owner of the file the M3U Tuner configuration can be saved.
It is also not a firewall permission issue, the LXC running jellyfin is allowed to access the DVB-C tuner.

The same error also appears if I try to save ...

• a random IP:Port combination as a HD Homerun tuner.
  
• the "LegalStream Live News Playlist", referenced in the Jellyfin Live-TV setup guide.
  

Therefore I think there is some sort of internal error in Jellyfin.
I even found a closed GitHub issue wich could be related to my issue but has not been answered by any dev: https://github.com/jellyfin/jellyfin/issues/9203


Kind Regards
TheHellSite