In case somebody arrives here with not changeable scaling issues, I want to add another solution:
If you have the file ~/.config/systemd/user/lomiri-full-greeter.service.d/override.conf, it may look like this:
[Service]
ExecStartPre=/usr/bin/dbus-update-activation-environment --systemd GRID_UNIT_PX=21
It overrides the deviceinfo value of GRID_UNIT_PX.
You could remove the override or adjust it to your needs.