I am in the opposite boat. I've been downloading individual songs I like since the age of 8 when I bought myself the cheapest Android tablet (€50).
I won't be spending my time to move to some online service.

And getting the music on other devices?
I can either play it through my laptop from phone using Bluetooth thanks to pulseaudio-bluetooth, and control the playback via KDE connect which can run over BT-PAN connection to save power, and is also more resilient to noise than Wi-Fi thanks to FHSS.
Alternatively, I can use LAN. All my music is on my phone (and a backup HDD + encrypted on cloud) and run a Navidrome server on my phone in Termux. This also goes for video which I serve from my phone using nginx with fancyindex module to make it nicer. Since I already have that, nginx acts as a reverse proxy to Navidrome. My music is sorted by folders, so to keep things simple I create m3u playlists that get autoimported to Navidrome. That part is pretty simple ls playlist-dir/* > playlist.m3u.

OK, perhaps the second part doesn't sound that convenient, but first part needs no setup with most distros. Perhaps installing KDE connect for music control (and more), but that is optional. Actually, the music control can be done just via Bluetooth, but I wasn't able to utilize my laptop's media buttons for that, and I don't want to have to mouse over to Bluetooth panel.

Same, Spotify and steam are too convenient for me. Everything else though...