Okay, let me clarify even more. :D
To this date, I have not been able to watch more than 5 minutes of a TV series, which I did to test Jellyfin weeks ago the first time, because it just bugs out at some point & cannot do anything, even after waiting hours just to see if it "finishes loading" as in good old YouTube days, where they would actually pre-buffer the entire video, given you waited enough.
So, as of now, Jellyfin is utterly useless to me, except for spoilers by automatically downloaded thumbnails, even though I disabled that feature during first time setup.
However, whenever I visit some Jellyfin Reddit to see the answers to a complaint similar to mine, people downvote the crap out of the complaint & say something like "it works for me, though", so I just assumed something's wrong with my setup.
Now, I'm starting to wonder, whether there's actually something wrong with Jellyfin & those downvoters are just fanbois who don't realise that their server is super powerful & can handle Jellyfin. 🤔