Can't install OS Update - 20GB wasted in APFS snapshots

I'm trying to update my OS from Big Sur. I had 16GB of free space available, but I can't install the OS update.

Looks like there are 20GB worth of APFS snapshots on my 120GB SSD drive. That's absurd.

This is what they are called, according to tmutil.

com.apple.os.update-51D425C3F73C05488FE6273A584E6DADB9CFAAD5AEB57007C65CE78C69F4AEE1 com.apple.os.update-MSUPrepareUpdate

How do I get rid of them? Lots of posts talk about using DiskUtility, but I don't seem to be able to do that. I turned off automatic Time Machine backups, and there don't seem to be any (none above have dates), but I'm still stuck.

And the free space keeps getting less and less and the APFS Snapshot volume appears to be increasing in size as I watch it.

What can I do?

Can't install OS Update - 20GB wasted in APFS snapshots
 
 
Q