After lengthy discussion with AI and numerous tries, we've concluded that:
Keep screen ON during lock — not allowed on Wayland GNOME
That goes for recent Zorin 17.3 and 18.
More details:
GNOME Wayland enforces:
if session is locked → turn display off immediately.
Same behavior in:
Ubuntu 22.04+
Ubuntu 24.04+
Zorin 17.3+
Fedora GNOME 40–46+
Debian Bookworm Wayland GNOME
Pop!_OS GNOME Wayland
This comes from Mutter/GNOME upstream:
They call it:
“Mandatory security privacy measure”
(They literally reject feature requests to keep screen visible while locked.)