Two drives and a USB drive connected to a hub, the hub connected to Mac Mini via USB-C after Sonoma install: the drives initially got a window saying they couldn't be accessed, then they would briefly appear, then a notification says they not ejected properly, and they'd disappear again. Then reappear again. And repeat.
Shutdown the Mac, unplugged everything from hub and re-booted. Then tried installing one at a time. Would seem to be fine, then t would all start over again.
Argh.
Shutdown the Mac, moved Hub input to regular USB. Rebooted. Then again, one after the other, I installed drives. Initially slow to acknowledge each drive, but all (eventually) accepted and seems fine now. Can access all of them, and they aren't disappearing.
Ain't tech grand?
PS: during all if this - and regardless of input method - two printers and camera also connected to the hub were seen and worked without issue.