Hello everyone, I immediately apologize for my English, I'm from the Czech Republic.
My PC specifications
motherboard : Asus P8H67-M ( BIOS LEGACY )
Processor: Xeon E3-1270 v2
Graphics Card: Amd Radeon RX 570 4 GB
BigSUR
The problem is this:
From the installation flash drive, the system loads normally and everything works.
But if you boot from the disk, then I have a black screen, but the system is running and there is a sound, if you wait until the computer falls asleep and turn it on, then everything will work