It's a hammer in search of nails. If you don't want transcoding it simply doesn't work. It's nice that it exists and works for some people, but I despise 'solutions' that have no reason to exist except the devs needing an excuse to do thins they like. If jellyfin had a normal, regular, honest and simple option to just turn off transcoding I'd probably switch to it (even if the library scan process takes days instead of seconds). I don't want to transcode anything ever, I use things in my lan, my devices can play all of the formats in my librabry - this is like archiving and unpacking every single file I move around on my pc.
Now plex is not opensource freeware nice things - it does what I tell it to do. That's about it
I can't disable transcoding globally, I have to mess with horrible config menus on every client I want to use. Library scans take more than 30 minutes on my i7-4790k NAS - after that I just stopped and removed the jellyfin server from it. Just being open source is not enough. Once it starts working as a user-first app I'll gladly switch over.