You can download Big Sur right now! Apple has fixed the "slow down," so it works now.
To install macOS 11 Big Sur, you need a: 12-inch MacBook (2015 and later) MacBook Air (2013 and later) MacBook Pro (Late 2013 and later) Mac mini (2014 and later) iMac (2014 and later) iMac Pro (all models) Mac Pro (2013 and later)
