I use jellyfin, is great for this and there are even phoone apps that can cache a certain ampunt of music on device.
I have also been bouncing around the idea of just coding some sort of playlist generator myself, I've been at this long enough that I'm pretty sure there's lots of public APIs to help me along as well as maybe some sort of huggingface routine, maybe.
I suspect that there's something ready-to-go, either Free or reasonably-priced, already out there and I just haven't looked at the right blog yet. I no longer assume that google represents anything remotely like the actual internet, and I don't know who does.