I’m using airsonic, a foss alternative to subsonic. It can have multiple accounts and shared playlists

I use bandcamp regularly, although i tend to just buy and download from the webpage, and then I let beets organise and copy the files into predefined directories. It also can do zip files.

As others have commented, stick with the Mac.
I recommend installing proxmox on it and run the apps you want. You can run pihole in a VM.
Do you need a NAS? Not really, but if you have cash available maybe get a used tower, use the disks you have and install TrueNAS. And this will only cost you max €200

https://www.alpinelinux.org/about/ Check out Alpine. Might just be enough for what you want

https://konstakang.com/devices/rpi4/LineageOS20-ATV/

Maybe this might be something to consider

There’s a community of people from Europe here that very much support a stronger EU and I believe in cooperation, unity and human values. Although, I still see the EU as a milder version of the US with a capitalist economic focus and I think this will not work in the long run.