I was on Jessie, did an upgrade to Stretch and then immediately to Buster. I believe I have the default gnome 3 desktop manager. If I lock the screen with super-l then I cannot wake the screen up again with the mouse or keyboard (but scroll lock/num lock do toggle the keyboard LEDs). This also happens if I do not log in after boot, the login screen auto locks after 5 minutes. I think the 5 minutes is coming from org.gnome.desktop.session idle-delay uint32 300, so setting that to 0 might stop it from auto locking, but that does not explain why it does not turn back on. Note that the machine does not suspend, just turns off the monitor. I believe I disabled suspend with org.gnome.settings-daemon.plugins.power sleep-inactive-ac-type 'nothing'. This is a desktop, always on AC, never battery.

I can bring the screen back over ssh with:

sudo systemctl restart gdm.service

Some gsettings that might indicate something:

$ gsettings list-recursively org.gnome.desktop.screensaver
org.gnome.desktop.screensaver picture-opacity 100
org.gnome.desktop.screensaver logout-enabled false
org.gnome.desktop.screensaver lock-enabled false
org.gnome.desktop.screensaver logout-delay uint32 7200
org.gnome.desktop.screensaver embedded-keyboard-enabled false
org.gnome.desktop.screensaver primary-color '#023c88'
org.gnome.desktop.screensaver idle-activation-enabled true
org.gnome.desktop.screensaver secondary-color '#5789ca'
org.gnome.desktop.screensaver logout-command ''
org.gnome.desktop.screensaver color-shading-type 'solid'
org.gnome.desktop.screensaver embedded-keyboard-command ''
org.gnome.desktop.screensaver picture-options 'zoom'
org.gnome.desktop.screensaver lock-delay uint32 0
org.gnome.desktop.screensaver show-full-name-in-top-bar true
org.gnome.desktop.screensaver picture-uri 'file:///usr/share/images/desktop-base/desktop-lockscreen.xml'
org.gnome.desktop.screensaver status-message-enabled true
org.gnome.desktop.screensaver user-switch-enabled true
$ gsettings list-recursively org.gnome.desktop.session
org.gnome.desktop.session session-name 'gnome'
org.gnome.desktop.session idle-delay uint32 0
$ gsettings list-recursively org.gnome.desktop.lockdown
org.gnome.desktop.lockdown disable-command-line false
org.gnome.desktop.lockdown disable-application-handlers false
org.gnome.desktop.lockdown disable-user-switching false
org.gnome.desktop.lockdown user-administration-disabled false
org.gnome.desktop.lockdown disable-printing false
org.gnome.desktop.lockdown disable-log-out false
org.gnome.desktop.lockdown disable-lock-screen false
org.gnome.desktop.lockdown disable-print-setup false
org.gnome.desktop.lockdown disable-save-to-disk false
org.gnome.settings-daemon.plugins.power power-button-action 'interactive'
org.gnome.settings-daemon.plugins.power idle-dim true
org.gnome.settings-daemon.plugins.power sleep-inactive-ac-type 'nothing'
org.gnome.settings-daemon.plugins.power sleep-inactive-battery-timeout 1800
org.gnome.settings-daemon.plugins.power sleep-inactive-battery-type 'nothing'
org.gnome.settings-daemon.plugins.power sleep-inactive-ac-timeout 3600
org.gnome.settings-daemon.plugins.power ambient-enabled true
org.gnome.settings-daemon.plugins.power idle-brightness 30


$ sudo -u Debian-gdm gsettings list-recursively org.gnome.desktop.screensaver
org.gnome.desktop.screensaver picture-opacity 100
org.gnome.desktop.screensaver logout-enabled false
org.gnome.desktop.screensaver lock-enabled true
org.gnome.desktop.screensaver logout-delay uint32 7200
org.gnome.desktop.screensaver embedded-keyboard-enabled false
org.gnome.desktop.screensaver primary-color '#023c88'
org.gnome.desktop.screensaver idle-activation-enabled true
org.gnome.desktop.screensaver secondary-color '#5789ca'
org.gnome.desktop.screensaver logout-command ''
org.gnome.desktop.screensaver color-shading-type 'solid'
org.gnome.desktop.screensaver embedded-keyboard-command ''
org.gnome.desktop.screensaver picture-options 'zoom'
org.gnome.desktop.screensaver lock-delay uint32 0
org.gnome.desktop.screensaver show-full-name-in-top-bar true
org.gnome.desktop.screensaver picture-uri 'file:///usr/share/images/desktop-base/desktop-lockscreen.xml'
org.gnome.desktop.screensaver status-message-enabled true
org.gnome.desktop.screensaver user-switch-enabled true
$ sudo -u Debian-gdm gsettings list-recursively org.gnome.desktop.session
org.gnome.desktop.session session-name 'gnome'
org.gnome.desktop.session idle-delay uint32 300
$ sudo -u Debian-gdm gsettings list-recursively org.gnome.desktop.lockdown
org.gnome.desktop.lockdown disable-command-line false
org.gnome.desktop.lockdown disable-application-handlers false
org.gnome.desktop.lockdown disable-user-switching false
org.gnome.desktop.lockdown user-administration-disabled false
org.gnome.desktop.lockdown disable-printing false
org.gnome.desktop.lockdown disable-log-out false
org.gnome.desktop.lockdown disable-lock-screen false
org.gnome.desktop.lockdown disable-print-setup false
org.gnome.desktop.lockdown disable-save-to-disk false
$ sudo -u Debian-gdm gsettings list-recursively org.gnome.settings-daemon.plugins.power
org.gnome.settings-daemon.plugins.power power-button-action 'suspend'
org.gnome.settings-daemon.plugins.power idle-dim true
org.gnome.settings-daemon.plugins.power sleep-inactive-ac-type 'nothing'
org.gnome.settings-daemon.plugins.power sleep-inactive-battery-timeout 1200
org.gnome.settings-daemon.plugins.power sleep-inactive-battery-type 'suspend'
org.gnome.settings-daemon.plugins.power sleep-inactive-ac-timeout 1200
org.gnome.settings-daemon.plugins.power ambient-enabled true
org.gnome.settings-daemon.plugins.power idle-brightness 30

Update

I edited /etc/gdm3/daemon.conf and uncommented WaylandEnable=false:

[daemon]
# Uncomment the line below to force the login screen to use Xorg
WaylandEnable=false

Now the screen comes up properly when I press a key. So it would seem it is something Wayland related. I have no idea on how to debug it or how to enable more verbose logging to try to narrow down the issue.

More info:

$ sudo lspci -nnk | egrep "VGA|3D|Display" -A2
0b:07.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] ES1000 [1002:515e] (rev 02)
        Subsystem: Dell PowerEdge T300 Embedded ATI ES1000 [1028:0210]
        Kernel driver in use: radeon