accideath

I second (third) an Intel ARC card. For the tasks you’ve named it doesn’t even really matter which one, even the smallest one is a transcoding powerhouse, doing multiple 4K transcodes with HDR tone mapping with ease.
Additionally, Intel drivers are wayyy better on Linux (TrueNAS) than Nvidia’s. Don’t even need to install them. I would go with any one you can get for a decent price, so probably the small A310. It doesn’t even need extra power. Sips like 30W or so.
If you want an upgrade still, A750s are also reasonably priced on the used market. Don’t get the A380 over the A310 unless they’re the same price. They perform almost identical and the 380 draws more power. Does also have more vram though, if you need that for immich.

And stay clear from AMD cards. They’re the goat for linux gaming but their video encoders are notably inferior to the other two. Not what you want for Jellyfin.

Sometimes, when I’m sick and have a bad cough, my lungs get itchy on the inside. It’s very frustrating.

Pretty much.
A few years ago I got an hp t620 thin client with an older AMD embedded quad core cpu for like 25€. I ran my home server on that for a while until I upgraded to something bigger.
You can still get the same device for pretty much the same price. You can even upgrade storage and RAM fairly easily (and cheaply, since it’s DDR3 and m.2 SATA).
And if CPU-Monkey is to be believed, it has about the same CPU performance as a RasPi 4 and 4x the graphics performance.