All the homepods are at version 17, however, you must consider that the Bose and Ropieee devices also went at the same time as the homepods. Roon was the very latest version. I even deleted it and downloaded again to see if that would clear the issue. All homepods are set to allow anyone on the same network, however, the ropieee(x2) and bose devices do not have that setting. Mac is version14.0 (the latest).
I have just started roon up on my 2011 trash can Mac Pro running Ubuntu 23.04 Luna LTS and that is showing all of the airplay devices and they work fine.
This is now fixed:
I logged out of the version of roon on the Ubuntu server and re-logged into the Mac Mini M1. All the airplay devices are back again! So this is definitely a bug in roon that logging out and back in again cleared some cache or something. Nothing else change in the 10 minutes on the network, airplay devices, os versions etc, since I logged out and back in again to the roon server on my Mac Mini M1.