LXQt settings aren’t used until after you’ve logged in and the LXQt session has been started.
If you want to use a different configuration at the greeter, you’ll need the greeter to know what keyboard you’re using, as it won’t be reading your LXQt setup.
Do note however GDM3 uses GNOME features to work (writing to the screen, getting input from keyboard); and isn’t supported by Lubuntu. You didn’t provide release details; but have you looked (https://packages.ubuntu.com/jammy/gdm3).
I think that dvorak-intl is not a layout, but a variant. I did not test it, but you should modify the file to something like:
Section "InputClass"
Identifier "system-keyboard"
MatchIsKeyboard "on"
Option "XkbLayout" "ir" # Please take here the correct layout, I am just guessing
Option "XkbVariant" "dvorak-intl"
EndSection