Yellow screen after installing. Radeon HD7770

Greetings and salutations. I got yellow screen with cursor after installing MacOS Big Sur, when trying to boot.

OpenCore 0.6.7

I3 3220; iGpu disabled; SMBios: iMac 15.1; Asus Radeon HD 7770.

Boot-argument: radpg=15. Without it i got just a black screen.