I've been trying to upgrade from 10.10 to 10.11 for a while now, as the Android TV app keeps nagging me, and every attempt ended with impossibly long library scan times.
After some thorough investigation, it appeared that a Home Videos type collection causes unending scan (yet to be solved), but also that Jellyfin does a lot of writes to the config directory (either database or metadata or both). Mine's on spinning media part of a ZFS pool. I tried a few performance tuning options, such as testing the config dir with recordsize (similar to block size) of 4K, 8K, 64K, 128K and library scans fell from 30-40 minutes down to 8-13min with 4K-64K. The ZFS tuning wiki suggest 64K recordsize with LZ4 compression for SQLite workloads such as Jellyfin. That seems to work as well as 4K and 8K but likely is faster when reading thumbnails and such.
Note that upgrading to 12-rc3, which is supposed to speed up library scans did not improve scan times for me. Optimizing config/database write speed did. I cross-checked the culprit by experimenting with moving the config dir to NVMe and RAM. Both of those got the scan times down to 8-9 minutes compared to the optimized spinning media's 12-13.
So if you had upgraded (or about to) to 10.11 your library scans are (about to get) dog slow and your Jellyfin's config dir resides on spinning media, optimize its write performance for SQLite.
They won’t do that because it’s expensive and free software generally doesn’t have the budget to do this
I don’t know why you think the “just works” is any different from tunneling with a service. Your server is still opened to the internet through upnp with direct connections and through a tunnel to plex.tv when a direct connection is not possible. In fact plex is inherently less secure because their infra is both the encryption endpoint (as opposed to your client with Jellyfin and Tailscale or whatever) and their infra has been vulnerable in the past (like the massive breach in 2022).
Jellyfin with something like nginx and a vpn is open to the internet, yes, but a service that tunnels (like wireguard, Tailscale) bypasses this issue and it’s up to you to set it up as to your level of comfort
Plex is just easier but as with all things tech (especially those infected with VC dollars) “ease” translates to less secure and far more likely to exploit your data