Hi the last suggestion fixed the problem. It works even with boot USB for clean installation. Thanks.

Hi @kh4inguyen, do you know if that solution works even installing Big Sur from USB from boot? Thanks

MacBook Air 2020 13'' - Running Catalina 10.15.7: Having the same problem at 12 minutes. Also, I created an USB for fresh install, but it stop and says: "to use this boot disk you need an update", I click on "update", but the problem persists. No way to install Big Sur. I tried the suggestion to reset the NVRAM, I tried also to stop FileVault. The only thing I haven't tried is reset of SMC. I don't know how tomorrow they can officially release. I tried to run the fresh install from USB in another MacBook Pro (2015), and there it's run.