Finally I solved my problem. Replacing the motherboard with Asus PRIME X470-PRO. I had to reinstall the OS because the hard drive started to fail (after logging in, the head constantly parked with a characteristic sound and reinstalling all the drivers did not help). After that, everything works fine. I noticed that the voltages are much lower compared to MSI. In general, as far as I know, all modern MSI motherboards have this problem, regardless of the chipset. Probably this can be corrected manually, but I don't want to dance with a tambourine trying to find the correct value for stable operation.
Thanks to everyone who tried to help.
Sorry to disappoint you but that is not all... I had a PRIME X470-PRO and replaced it with a MSI x570-A PRO and both have same behavior. Black screen with cursor before POST beep. High BIOS time on Windows Task manager and for me at least, worst of all: Deep sleep bug (even with latest agesa-v2 1.8...
Our main similarity: Ryzen 2700 Series.
so far I've tried:
CMOS Reset, Mainboard replacement. Windows clean install (also without any peripherals). BIOS Downgrade. single channel ram. setup outside the case to exclude short-circuit.
Asus support insists it has to do with my PSU being older than 7 years old... Never failed on my previous setup i5-5500k
A friend of mine also owns a 2700x. Deepsleep doesnt occur on his setup. Slow Boot timing is pretty much the same as mine (20sec +).
I might try Ryzen 3, otherwise, idk.... might send AMD my power bill for not being able to send the pc into sleep
Asus x470-prime pro / MSI x570-A pro
Gskill 16gb (2x8GB) DDR4-2132 (1066) default/xamp1/2
Asus RTX 2060 Super
Corsair 650w 80 PLUS Bronze