

For my first server, after moving on from 2 raspberrys to a Proxmox host, I went with an embedded Asrock MB, passively cooled so you know it wasn’t drawing much power, still had multiple SATA ports and with the right sticks I could get 32GB RAM in.
Seems better to me than a minipc where you have no expandability, especially no chance for RAID.
Well TBH my familiarity with Jellyfin is rather limited, I installed it, it works, I don’t mess with it.
The only problems I’ve had is when some friends had trouble logging in, which was solved with a cache and cookies cleanup. At least the only problems I know of: turns out my friends don’t complain when it doesn’t work.
I know that Jellyfin CAN serve without transcoding (you can disable it on a per-user basis IIRC), but as to why it decides you can’t, I have no idea. Have you tried filing a bug report? Sometimes it’s a bug, sometimes they give you a solution. Sometimes both.