So I decided to go to Big Sur on my MacBook Air 2017, which is not my primary machine. I started out from the Bay Area and headed south to Monterrey....wait, wrong trip!
I downloaded the update and proceeded to install. After a few hours it stalled out and I called Apple Support. They had me force power down while holding several keys (cmd/shift/option...who remembers and then hitting the power again and within 30 seconds the progress bar finished and there I was in Big Sur. Now to get familiar with things. Maybe tomorrow I'll update my 2020 iMac.
Asheville, NC Area