KDE 5.19.4. After recent mesa update I'm getting:

"Failed to create OpenGL context: Could not create GL context: BadValue (integer parameter out of range for operation)"

when launching some games, e.g. Factorio. I tried waiting couple of days for an fixed update - nothing. Reinstalled manually my AMD mesa drivers - nothing.
Any tips how to fix it?

This would not be a KDE issue at all, but one with your distro's driver update, and/or the game(s) in question.
KDE doesn't supply your mesa drivers or OpenGL implementation.