Best ways to watch
The Jellyfin project maintains a set of clients for various platforms
📄️ Browser
Browser playback generally isn't recommended. Firefox doesn't support H.265 at all - which means no movie will play there. Chrome and Edge do support H.265 - so they might work fine for you.
📄️ Desktop
Jellyfin Offical Desktop App:
📄️ Mobile
Android
📄️ TV
Android TV