To me, this issue has became a classic for some reason. Not sure it has to do with silicon-based minis, i have an intel-based 2018 and i am stuck with that issue since over a year (more or less two latest macOS versions). There is no reason: my drives have their own power supply, my usb hub has its own power supply. I replaced that hub indeed, thinking it might be at fault.
I tried the hub into a different usb port on the mac mini (there were plenty then: 2 usb3 ports, 4 usb-c/TB ports.
i’ve learned to be patient, force-connect one when i really need it, then forget it otherwise. The issue then is - if you use any third party backup like Backblaze - you will receive updates telking you it was not able to complete that drive’s backup. (This is annoying, as that 3rd party really once saved my a.. while iCloud drive had just erased very important work forever for one-second mistake on my part, but i’m getting out of topic).
Even the separate Time Machine drive is kicked out randomly- i’ve been weeks without it being able to complete a backup.