A Microsoft file hosting and synchronization service.
I Agree it seems there is no definitive solution to the problem. The best I managed was a workaround.
In my case I have a 256 GB disc in the Mac, and I purchased a 2TB external disc.
I now have OneDrive on that external disk, and keep all files downloaded on that disk, so I am not relying on the OneDrive ‘space saving’ feature.
I have a Mac Mini, so having a permanently attached external disk is ok for me,
And having all files downloaded means that I have a copy of all the files locally as well as in the cloud.
Fusers with MacBooks, I appreciate this is not viable even as a workaround.
But the first thing is to clear that space used by OneDrive so the Mac can function normally.
From my original post....
Unlinking the account shows the 'hidden' space that OneDrive was using. Nearly 120GBs in my case.
Update:
I decided to try and clear down all of the hidden used 'update' space following unlinking the account.
I installed the MacPaw CleanMyMac X software to try and do this.
I went though all the clean up steps that that product offers, which helped me free up a lot of disk space, but it did not clear down the space left as 'other' after unlinking one drive.
So I rebooted. After reboot all this 'other' space disappeared.
It is not clear whether CleanMyMac, or the reboot, or the combination of both was needed to clear the ‘other’ space.
CleanMyMacX, however, was very helpful analyzing disk space usage.
Another nightly recommended utility is DaisyDisk, https://daisydiskapp.com/, which is quite a bit cheaper than CleanMyMacX
I can’t confirm if the current MacOS version helps solve the issue as I have not experimented further with OneDrive