I think my mistake was that upon the beta6 update not being available for download, I was impatient and tried turning beta off hoping when I'll turn it back on, the update will be available. But after turning beta off the Software Update tab entered into a state when simply there is no beta option anymore (just like for others here). On an other Mac (same IP, same beta OS version, both M1) I was careful not to turn the beta off when the update was not available - simply had to re-enter my developer credentials and beta6 popped up right away.
UPDATE: Fixed!
UPDATE: Fixed!
Last edited: