Comment # 3 on bug 109122 from Matej Lach

I can confirm this bug is indeed present. 
Worth noting that the screen is only blank on the laptop built-in display,
(after KMS), external monitors work fine. 

Adding `amdgpu.dc=0` to the kernel parameters resolves the issue for me, but
this was not necessary before kernel 4.19.9, so it seems like a regression. [1]
seems related.

1 - https://bugzilla.kernel.org/show_bug.cgi?id=200695