Easy to do, yet scary if you only have one computer.
Download the latest version of Patched Sur.app
Hit Create Installer
Follow the instructions
At the end (restart time)
Do not restart, shutdown your mac
If you restart, mac boot may not catch option key
Hold down option key, turn on mac with the power btn
select EFL boot, keep holding down the option key – wait a while
Just install Big Sur
Go for a walk – this may take a long time. It seems to stop sometimes – just leave it alone.