SC on iOS, iPadOS & Apple TV

For iOS, iPadOS & Apple TV usage, I'd highly suggest Infuse.
Yes, it's a proprietary app but the free version is more than enough for SC.
The reason I don't recommend the official Jellyfin app is because, like most other OS, iOS & iPadOS doesn't support MKV containers with formats such as HEVC. (it can, but it doesn't, end of discussion). Plus, Infuse do support a ton of good features.

Get the app on App Store. Open the app, tap on Settings.
Add Files. Scroll all the way down to 'Media Servers' and tap on Jellyfin.
Enter SC's address, account details, and proceed. Select all the libraries you'd want to sync and just wait a minute or two for it to do so - and that's it!

For more detail guidance on connecting to any Jellyfin/Emby/Plex instance, refer to this guide from Firecore, the company behind Infuse:

https://support.firecore.com/hc/en-us/articles/360006462093-Streaming-from-Plex-Emby-and-Jellyfin