I'm sorry that you have had a bad experience.

I have been running Jellyfin in a container on a Linux server for three years now. I am streaming video to Infuse on three Apple TV boxes and music to a Kodi installation on a Raspberry Pi with no issues.

I'm been running Jellyfin in a container as well for 4 years. I stream to a couple Roku devices. The only problem I've encountered is Roku doesn't support DVDSUB and Jellyfin recently added automatic overlaying of DVDSUB server-side which drastically slows down seeking on Roku.