Had a hard time to update Sonoma to RC 2, OTA did not work, the download did not finish even though macOS reported so, it later could not verify.
So, I created a USB installer, that worked, this was only a few days ago.
So, next I tried it the same way, OTA did not work, recreated the USB installer multiple times but the install got bogged.
Update installer couldn't verify, it took quite a bit of time after starting to get to this point.
Not able to start from Sonoma either, and, the original disk (name = MacMini) vanished, I could only choose the MacMini-Data disk.
Eventually I decided to use a slow (128GB) SD card, now, that worked.
Wow, now it seems...no, it is a lot faster than before, all seems to work, even Bluetooth, had trouble last few day, Trackpad and Keyboard did not show up.
Thanks to the great developers, cheers to them.