Yeah there are plenty of apps that can rip from tidal, apple music, etc. noteburner, deemix, deezloader, musify, notecable, and noteburner are all ones that I tried where they successfully ripped audio from streams to flac but spectrals showed the flac was transcoded from lossy source.
Granted this is basically inaudible and super nitpicky, like honestly show me the person who can truly hear the difference between a modern 320 mp3 and a 16bit flac in a double blind situation. But if you’re using these rippers to upload to a private tracker, especially a popular release, guarantee someone will check
That said streamrip can get deezer 16 bit, 24bit tidal mqa (which isn’t actually lossless), and 24/192 qobuz but you need a premium account and things break from time to time
https://github.com/nathom/streamrip
Apple music remains a very closely guarded secret although I recently saw this: https://github.com/zhaarey/apple-music-downloader . I have to create a burner and vm to play with this though bc it’s pretty sketch
On device isn’t always ideal. I don’t use immich because i don’t have a large photo library. But I do use komga. Nextcloud can sort and manage epub/pdf like komga but as poVoq said, the specialized solution is superior
This point is where on device app is not the ideal situation, for me at least. These apps exist. Tachiyomi and the resultant forks can import a local library. And frankly even a somewhat massive local library can fit on a cheap SD card
The point of the server is portability. With this I have portability across my devices. My library, reading status, metadata, etc is available on all devices. I can read a book on my ereader, close it, the status is synced. I can pick up from my laptop and the same thing occurs. I can pick up from my phone, download the book to my device, and keep reading while I’m away from home. If I wanted to I could open remote access to my server and avoid the need for downloading the books but that’s a whole thing
I don’t think it would make sense to run a server solely for this but it’s a service that doesn’t take much in terms of resources and I read a lot.