As I do have ALL my music locally stored (about 100 Gigs) I started to use my 256GB iPad as a streaming device for now.
I often use the HomePod for listening to radio stations. It is really interesting how many different stations Siri can play, if I ask for "Radio Ten" (example) - or even does not find that station at all in my library ?
As an alternative - without Siri though - Sonos creates a database from your local library (not iTunes libary) and can play your music directly from a cheap server. You will have to access it from the Sonos app, but it does not Airplay from that device. Airplay is possible, but not mandatory.
Concerning Sonos: I was kind of astonished, Apple does sell Sonos now as a regular offer in their stores, offering HomePod as their own product at the same time. It seems to be a valuable alternative for Apple...
As a big fan of the HomePod system I have to admit that Siri is the weak point when wanting a specific piece of music. Anything that has any complication in the title becomes very challenging for my squat little friends.
To solve my most oft used "complicated" music to include Classical, i have created playlists with those songs with "easy" titles. Doesn't solve the Ops real problem of "hey I want to listen to a particular piece of music by a particular orchestra, recorded at a specific time" on a whim. That is where Siri show's it's weakness.
If not for automation (still f'in buggy, but whatever) I would have jumped on Sonos as well, in fact with unlimited resources i would have a few Sonos in certain rooms just because, but that is not the case. I am in too deep at this point, but I would not shy away from Sonos if I was purely wanting music
I did see Sonos is back in the Apple store, assuming it is a BT speaker that makes sense. That is a feature that would have been huge IMHO and brought more to the HomePod game. I have a JBL Flip thing that I use in my garden, doesn't sound "great" but is better than my iPhone speaker and waterproof, etc.
Radio is unexplored for me, but have automations to turn on lights in the AM and play a news channel that I favor, works pretty well.