Display does not turn on after DPMS turn off after upgrading to 4.18.5

Environment

• OS: ALDOS 1.4.18 (basically a Fedora fork without SystemD)
• Xfce4-power-manager 4.18.4
• xfce4-settings 4.18.5
• libxfce4ui 4.18.6
• libxfce4util 4.18.2
• gtk3 3.24.42
• glib2 2.72.4
• gcc 8.5.0
• glibc 2.27
• upower 1.90.2
• Display: A 24 inches Samsung LED display connected via HDMI to an integrated AMDGPU card.

Upgrading to xfce4-settings 4.18.5 made my display to turn off via DPMS (after the time set in xfce4-power-manager-settings or going to hibernate or sleep mode) and kept that way (no turn on), no matter what I did, until I acceded from another machine and killed the X server (init 3) and start a new session (init 5).

Initially assumed it was something in xfce4-power-manager 4.18.4, but downgrading this package, did not solve the issue. So, instead upgraded again to xfce4-power-manager 4.18.4 and I tried downgrading xfce4-settings to 4.18.4, and well... magically the issue was solved.

If using xfce4-settings 4.18.5, I had to disable Display Power Management to avoid display to turn off. No matter what I did, if I let the display to turn off, it dit not turn on again, rendering my PC unusable unless killing X server via SSH.

There are no relevant/related messages in ~/.xsession-errors, but I found this at /var/log/Xorg.0.log.old and other Xorg.*.log files generated during testings.

[  4320.871] (EE) AMDGPU(0): drmmode_do_crtc_dpms cannot get last vblank counter

Somehow, seems the blame is on 4f10cc8f or 6e37f3c6, the only relevant and related commits.

Again, downgrading to xfce4-settings 4.18.4 solved this issue for me and display works (turns off/on via DPMS) as expected and no relevant errors appear again in /var/log/Xorg.*.log*.