I used Windows 10 Update Assistant to upgrade to 20H2 from 2004 and it took over 1 hour to complete. The download and install in Windows took 5mins but upon rebooting it took an hour updating. The progress stuck at 26% for about 20mins, went to 48%, then 64% and back to 60%. This is curious, considering we are told this is a fast update. I can only conclude that it got stuck on verifying some driver during the reboot. The update wasn’t offered in Windows Update, so maybe it is always best to wait for that.