My Big Sur installation on my Mac Pro 5,1 was on an external eSATA SSD. Worked great.
Last night night Catalina crashed during sleep (as it occasionally will.) On reboot this morning the "BigSur/BigSur-Data" disk showed up as "Big Sur" (the original APFS Container name prior install.) Contents were erased. As a secondary system it was not backed up, hours down the drain. I tried repair from another Big Sur installation, but there was nothing found.
After reinstall I will leave it turned off, when not in use.
Last night night Catalina crashed during sleep (as it occasionally will.) On reboot this morning the "BigSur/BigSur-Data" disk showed up as "Big Sur" (the original APFS Container name prior install.) Contents were erased. As a secondary system it was not backed up, hours down the drain. I tried repair from another Big Sur installation, but there was nothing found.
After reinstall I will leave it turned off, when not in use.