Well, here is the relevant part then, sorry if it was not clear:

• Jellyfin will not play well with reverse proxy auth. While the web interface can be put behind it, the API endpoints will need to be excluded from the authentication (IIRC there are some examples on the web) but the web part will stil force you to double login and canot identify the proxy auth passed down to it.
• Jellyfin do support OIDC providers such Authelia and it’s perfectly possible to link the two, in this case as i was pointing out, Jellyfin will still use it’s own authentication login window and user management, so the proxy does not need to be modified.

TLDR: proxy auth doesnt work with Jellyfin, OIDC yes and it bypassess proxy, so in both cases proxy will not be involved.