This is misinformation.

I run my jellyfin behind reverse proxy and use SSO pretty well. There is a OIDC plugin for jellyfin that just works with your preferred SSO.

Indeed Plex is easier to use, and manage all that for you, but this is self hosted community after all, there is smart people capable of running a reverse proxy and a proper SSO.

For the others, Plex indeed is forth paying for (?).