My own use for OneNote was mainly drawing/hand written notes using a drawing tablet. For that use case, I have replaced it with Xournal++
For other notes written with the keyboard, I use simple local markdown files.
All my notes are synced between computers with Syncthing
Spotify at least does allow you to add local files on a computer, and they even sync tracks to your phone when they are on an offline playlist when the devices are on the same network. I’ve done that myself to get some otherwise unavailable songs into my catalogue, and am thinking of starting the move to owning all my music that way