I successfully did it about 2 years ago, following the instructions from this repo (last commit 2 years ago though…) https://github.com/MMMZZZZ/Jellyfin-Migrator

I’ve been using Fladder on my steam deck, it allows downloading for offline play. Works pretty well but the interface is too mobile centric IMO.

There was Jellyflix which had a similar feature but it wasn’t straightforward to get running on Linux. Haven’t checked it since!

Oh I got one from when I was a kid: my sibling’s friend once valled her an “invertebrate brain”. I’m glad she didn’t have any vertebrae in there!