Not sure if it's related, but with  4.20.0-rc6 the regression when monitor goes
to sleep before reaching sddm is back. It's erratic, i.e. doesn't happen on
every boot. And I do see this REG_WAIT in dmesg when it does.

Turning monitor off and on, then going to tty and restarting sddm works around
it.

Similar bug was fixed in the previous kernels, so I wonder if the fix for this
one somehow brought that issue back.

GPU: Sapphire Pulse Vega 56.