I had to downgrade back to Catalina from Big Sur, so I have a clean Catalina installation and my HD shows:
Capacity: 250 GB
Available: 23 GB
Used: 42GB
Why is only 23GB available? I can't find all the mysterious data taking up the space, OmniDiskSweeper doesn't see anything either.
MacBook
How much free space did you have before the downgrade? Knowing the scale of the issue may make diagnosis easier.
Does the Trash need emptying? It's common after doing a system upgrade of downgrade for the process to move unneeded components to the Trash, but emptying Trash is not automated.
Also look in your Applications and Downloads folders to see if an installer file (or two) is still hanging around. That can use a massive amount of space.
How much free space did you have before the downgrade? Knowing the scale of the issue may make diagnosis easier.
Does the Trash need emptying? It's common after doing a system upgrade of downgrade for the process to move unneeded components to the Trash, but emptying Trash is not automated.
Also look in your Applications and Downloads folders to see if an installer file (or two) is still hanging around. That can use a massive amount of space.
Before the downgrade I could account for all my HD space, I had about 120 GB free. The trash has been emptied and my downloads folder is empty. I can't see anything unusual in the Applications folder either. I have gone through each folder separately, in total I have very little taking up space when looking at the folders, but there is some hidden files taking up about 185 GB of space. An 'update' HD appeared on my desktop after the downgrade, but it is empty.
disk space missing after downgrade
