If it works, I don’t update unless I’m bored or something. I also spread things out on multiple machines, so there’s less chance of stuff happening like you describe with the charts feature going away. My NAS is pretty much just a NAS now.

You can probably backup your configs/data, upgrade, then deploy jellyfin again, restore, and reconfigure. You should probably backup your data on your ZFS pool. But, I recently updated to the latest TrueNas Scale from ~5 year old FreeBSD version of TrueNas and the pools still worked fine (none of the “apps” or jails worked, obviously). The upgrade process even ported my service configurations over. I didn’t care about much of the data in the pools, so only backed up the most important stuff.