Well, in clover boot into recovery. When booted, select from menu Utilities > Terminal. cd to /Volumes/<DiskName>/Library/Extensions. You can check it issuing 'mount'. Remove all NVDA* and Ge* in the folder (10 of them in total). Reboot
Upgrade ran relatively smooth. It fails to load after reboot due Nvidia drivers. I had to boot into recovery, run shell and remove NVDA*.kext and GeForce*.kext in /L/E. After that it booted ok. Everything seems to be ok, including audio.