I use Jellyfin to host my music, and Finamp on my phone to browse and listen to it. Finamp supports downloads as well, so you can listen to your music offline and away from home. Pair that with a self-hosted VPN to access Jellyfin away from home and you’ve got most of your needs covered!
The real answer? Buy a phone older than the 15. You’ll never get on-device intelligence. My 13 Mini takes great pictures, performs perfectly, has great battery life as a non-gamer. And it should get at least 3 more years of iOS updates (maybe more? phone specs have really leveled off).
Anything newer, Apple and Google will start pushing intelligence on you simply because your phone can do it.
You could try GrapheneOS as well on a recent Pixel.