Restore mac Mini with a semi-recent backup
I upgraded my very old mac Mini to Catalina, which is the most recent macOS supported for the device. I now wish to restore to a point in time a couple of months ago just before I upgraded from Sierra (10.12) to Catalina (10.15).
When I boot into recover mode (⌘R), I can recover only using backups taken after the upgrade to Catalina. When I try to restore using the latest backup for Sierra, it complains saying...
The system can't be restored onto this disk because HFS systems can't be restored to space sharing APFS volumes. Reinstall macOS on this disk and then use Migration Assistant to transfer data from your backup instead.
When I use Disk Utility, I see that the Macintosh HD filesystem type is APFS (expected). I guess when I upgraded to Catalina, the filesystem type was changed from HFS to APFS.
Do I really have to reinstall Catalina (but use HFS for the filesystem type) or can I use Disk Utility to reformat the hard drive using HFS?
After all, I don't think I care what's on the hard drive right now. And, frankly, I don't recall if I can choose the filesystem type (APFS might be forced). But that's why I'm asking now rather than later after I supposedly would make yet another mistake.