I'm still getting "the requested version of macos is not available", and I've been trying for days. This is on my 2013 iMac. I have to search for it explicitly in the App Store. Then once I find it and press "Get", it takes me to system preferences with that error. The App Store listing says its compatible with my Mac.
My 2013 MacBook Pro was able to update ok to Big Sur a few days ago.
I read a post on here to disable auto-update to fix this issue. I did, but still get the same error. I also did a google search and the posts were mostly saying this was an apple server error (on Thursday) and has since been resolved.
Any ideas? Thanks.