IMO, you want ram more than you want processing power. 16 gig ought to be enough. Most of the time your containers will sit dormant and just consume memory. However since you want to run Jellyfin, get a recent CPU which can do hardware decoding of popular codecs. There’s charts online that show what generation can handle what codecs. Ideally you don’t want that done by software. You should still be able to find something cheap.

In terms of placement. It depends a lot on noise IMO. If you’re running something small without magnetic storage, you’re probably fine to stick it anywhere. If you have several data-centre grade hard drives, you will probably want to keep it somewhere where you wont hear it all day.

In terms of upgrading, I’m not sure if its as much of a concern as you might think. I run probably about 30 docker containers off a NUC clone and a seperate NAS, and that has worked pretty well for the last few years. I can always add more drives to the NAS, but otherwise its fine. Also, many of my services scale to zero with sablier+traefik, and I schedule filesharing for low bandwidth times. This makes things pretty manageable.

I did the same but joined Tidal for the same reason. Their app isn’t terrible—could do with more features but it’s been robust in my experience.

I’m aware. You may have missed that I made that distinction in my first sentence.

With modern Usenet there are about 8 or so backbones used for file sharing. Your Usenet provider/server would connect to one or more of these backbones.

Its true Usenet is designed for federation, and in the 80s and 90s it was thousands of servers but today commercial Usenet providers just resell these 8 backbones.