Im not sure what the previous kernel would have to do with this, but I don't use the Pi's.
Are you sure your external drives were powered on, and not asleep? Make sure they are powered on, then either via ssh or console, log in as root and type mount -a and see if they show as available in the gui after a refresh.
I wasn't aware it was a Pi. In my case, my raid card drivers are not loading on the most recent kernel, 5.8 but work fine on 5.7.