Hello. First I switched my build from Clover to Opencore 0.6.3 using the same OS install. This took me some time as I was completely ignorant about Opencore, but after several hours I succeed in migration to Opencore 0.6.1, then update to 0.6.3 and finally Updating from Catalina 15.7 system preferences.
Update was very smooth, actually like a real Mac. Just press the button and leave the system on its own. After 20 minutes +- I got the Big Sur welcome screen.
No issues known at this moment.
My build is with Gigabyte Designare Z390 and AMD Radeon 580
I updated also. Everything seems to work just fine except sleep. It goes to sleep but it won't wake up. Sometimes it will wake up but show blank screen so I have to reboot and sometimes it will display the login screen but it doesn't respond to the keyboard or any mouse clicks. I 've tried a couple SMBIOS (iMac 15,1 / 19,1 / 19,2 an 18,something) but still no luck. Sleep used to work from the days of High Sierra.
I am using the latest clover and at first tries I was getting the EB|LOG timestamp error so after searching a bit I set SetupVirtualMap to true in clover configurator and so I managed to complete the installation (it took a while, a few times I thought it was stuck). Also I updated AppleALC, Lilu, VirtualSMC and WhateverGreen.