Screen suddenly waking up for unidentified reason

Ever since upgrading dom0:

Packages Altered:
Upgraded python3-qubesdb-4.0.15-1.fc25.x86_64            @qubes-dom0-cached
Upgrade                  4.0.16-1.fc25.x86_64            @qubes-dom0-cached
Upgraded qubes-db-4.0.15-1.fc25.x86_64                   @qubes-dom0-cached
Upgrade           4.0.16-1.fc25.x86_64                   @qubes-dom0-cached
Upgraded qubes-db-dom0-4.0.15-1.fc25.x86_64              @qubes-dom0-cached
Upgrade                4.0.16-1.fc25.x86_64              @qubes-dom0-cached
Upgraded qubes-db-libs-4.0.15-1.fc25.x86_64              @qubes-dom0-cached
Upgrade                4.0.16-1.fc25.x86_64              @qubes-dom0-cached
Upgraded qubes-input-proxy-1.0.20-1.fc25.x86_64          @qubes-dom0-cached
Upgrade                    1.0.23-1.fc25.x86_64          @qubes-dom0-cached
Upgraded qubes-input-proxy-receiver-1.0.20-1.fc25.x86_64 @qubes-dom0-cached
Upgrade                             1.0.23-1.fc25.x86_64 @qubes-dom0-cached
Upgraded qubes-release-4.0-8.noarch                      @anaconda/rawhide
Upgrade                4.0-9.noarch                      @qubes-dom0-cached
Upgraded qubes-release-notes-4.0-8.noarch                @anaconda/rawhide
Upgrade                      4.0-9.noarch                @qubes-dom0-cached
Upgraded python3-blivet-2:2.1.11-6.fc25.noarch           @anaconda/rawhide
Upgrade                 2:2.1.11-7.fc25.noarch           @qubes-dom0-cached
Upgraded python3-xen-2001:4.8.5-28.fc25.x86_64           @qubes-dom0-cached
Upgrade              2001:4.8.5-29.fc25.x86_64           @qubes-dom0-cached
Upgraded xen-2001:4.8.5-28.fc25.x86_64                   @qubes-dom0-cached
Upgrade      2001:4.8.5-29.fc25.x86_64                   @qubes-dom0-cached
Upgraded xen-hvm-2001:4.8.5-28.fc25.x86_64               @qubes-dom0-cached
Upgrade          2001:4.8.5-29.fc25.x86_64               @qubes-dom0-cached
Upgraded xen-hypervisor-2001:4.8.5-28.fc25.x86_64        @qubes-dom0-cached
Upgrade                 2001:4.8.5-29.fc25.x86_64        @qubes-dom0-cached
Upgraded xen-libs-2001:4.8.5-28.fc25.x86_64              @qubes-dom0-cached
Upgrade           2001:4.8.5-29.fc25.x86_64              @qubes-dom0-cached
Upgraded xen-licenses-2001:4.8.5-28.fc25.x86_64          @qubes-dom0-cached
Upgrade               2001:4.8.5-29.fc25.x86_64          @qubes-dom0-cached
Upgraded xen-runtime-2001:4.8.5-28.fc25.x86_64           @qubes-dom0-cached
Upgrade              2001:4.8.5-29.fc25.x86_64           @qubes-dom0-cached

my screen (iMac 14,1) wakes up for no obvious reason after being put to sleep (off) by issuing sleep 3; xset dpms force off

Xorg.0.log tells me nothing, where should one hunt for dpms triggers?
I’m using i3, without any active screenlocker or screensaver.

Things tried: upgrade xorg-x11-drv-intel from testing (2.99.917-49.20210126), to no avail. Next: downgrading qubes-input-proxy(-receiver) in dom0.

Downgrading qubes-input-proxy-* in both dom0 and usb qube did nothing. Trying GUI related packages next:

qubes-gui-dom0 ?

I’m just guessing really.

No dice. Would anyone using i3 be so kind and try the following in dom0 terminal, with screensaver and locker disabled:

sleep 3; xset dpms force off

And wait a bit. Sometimes my screen flips right back on, sometimes after a second or 8, leading me to think the culprit is programmatic. No interaction, no active peripherals prior to screen wake-up. What could be causing this insomnia?

Running kernel 4.19.155 instead of 5.4.88 in both dom0 and vm makes no difference.

Issue not bound to i3, happens with xfce too.

Downgrading qubesdb packages in dom0 and vm to 4.0.15 does not affect the issue.

xev shows no X events during screen-off-time.

Downgrading xen packages in both dom0 and vm does not solve the issue. Need lower level power-management logs!

Shutting down the Xfce 4 Power manager xfce4-power-manager --quit (dom0) allows for my screen to remain off, so we’re getting closer. Upower seems dormant, what else manipulates power management?

Somewhere around the time of the aforementioned dom0 upgrade I must have accidentally enabled Presentation mode by right-clicking the Xfce widget. When disabled:

TRACE[xfpm-dpms.c:337] xfpm_dpms_inhibit(): dpms inhibited FALSE