With 2 monitors (one on VGA, one on DVI-D), screen turns black while loading
system in console
When only 1 monitor connected to VGA everything is fine.

There is no problem with kernel 5.2 or with amdpgu-dkms 19.10 on debian buster
(linux 4.19)

It happens only with amdpgu-dkms 19.20 or 19.30 (on debian buster - kernel
4.19)
For 19.20 I applied my patch from
https://bugs.freedesktop.org/show_bug.cgi?id=111103, which is merely the same
as the code in 19.30