Big Sur "Unable to check for updates" workaround doesn't work.

I see this message in software update:

Unable to check for updates
No available updates found. Please try again later

The workaround in the release notes did not work.

Anything else I could try?
The workaround from the release notes (search for "Installer and Software Update") - worked for me - for a little while. Now I'm getting the same error again.

Re-doing the workaround didn't help.
Yep, I met the same problem. You cannot install the Big Sur system by covering the Catalina. I think Apple should release a software to help us to handle this problem.
Big Sur "Unable to check for updates" workaround doesn't work.
 
 
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