Also a Plex lifetime user. I tried jellyfin not too long ago to see what the fuss was all about. I had heard that they handled her tonemapping better.
The interface is different but more or less just as good as Plex. It’s definitely more for the person that likes to dive in the details of the config of their server. For example, you need to setup your own domain for external users to connect to. It’s not done automatically like on Plex.
The focus on your content vs the “free” content Plex shoves in our face is nice I must admit.
Just a question of preference. In the end I stuck it out with Plex… For now.
Is it giving you any kind of on-screen message? What about the logs? Is this Direct Play or Transcoding?
I know some players don’t handle HDR very well, but that’s usually related to bad tonemapping.