When I encountered a similar situation I tried with the ikea speakers (Sonos Based) and I couldn’t get them to work without the sonos app, so I returned them.

I figured that a solution could be having, in each room, a mini-pc (RPi or similar) running RuneAudio and a set of speakers connected via audiojack.

I tried with 1 room and the proof of concept seemed to work, but didn’t invest on getting the rest of the house work.

In the end went for a couple of portable Bluetooth speakers to have floating around the place. Cheap and simple