Is spotube just another client for Spotify? Or what does it do? How is it getting rid of Spotify? You could host navidrome on your NAS and access it via webbrowser. If you don’t like the interface, there are several subsonic alternatives.

I paid around 200€ for a used HP OEM desktop machine. It got a i7 9700 and 32 GB of RAM in it. Still idles at a pretty low power consumption. But I never have to worry about resources, haha. I come from a long history of windows, just recently switched one of my main PCs over to Linux. I like a GUI, still. I got unraid for my server, back when the lifetime licences were still the norm. Makes it really easy to manage services, especially in conjunction with storage (say Immich or Navidrome). Containers and VMs are managed via a GUI and super easy to set up. I work IT-adjacent, but I’m far from being as professional as probably most people here, so this works fine for me.