Can't install Big Sur on My Passport for Mac "missing a firmware partition"

Brand new M1 Mac Mini and trying to create an external bootable drive on a My Passport 4TB. Followed instructions to Erase Volume with Extended (Journaled) and GUID Partition Map but when I select the drive in the Big Sur installer it says "you may not install to this volume because the computer is missing a partition".

Is this a problem with the drive? Does it need a firmware update? Is there another brand of drive that will work? I've Toshiba isn't as big as I want but that comes up as selectable.