(In reply to Jerry Zuo from comment #35)
> "startup monitor sleep regression". Please give more details on that. Thanks.

This behavior used to happen in the previous kernerls but got fixed at one
point. Now it's back.

Basically, after GRUB, the system boots (I usually enable loglevel=4 to see
system output), but right before reaching graphical login (sddm in my case),
the monitor simply switched to sleep mode. To work around it, I have to:

1. Turn the monitor off and on.
2. Switch to tty1, and restart sddm from there.

This enables graphical login.