Disabling portals for greeter user

[ossimoi]

When regreet starts, it activates xdg-desktop-portal via d-bus. I assume this comes from gtk4.

Sep 24 06:51:43 host dbus-daemon[5532]: [session uid=396 pid=5532 pidfd=5] Activating via systemd: service name='org.freedesktop.portal.Desktop' unit='xdg-desktop-portal.service' requested by ':1.0' (uid=396 pid=5526 comm="regreet")
Sep 24 06:51:43 host systemd[5481]: Starting Portal service...
Sep 24 06:51:43 host dbus-daemon[5532]: [session uid=396 pid=5532 pidfd=5] Activating via systemd: service name='org.freedesktop.portal.Documents' unit='xdg-document-portal.service' requested by ':1.2' (uid=396 pid=5535 comm="/usr/libexec/xdg-desktop-portal")
Sep 24 06:51:43 host systemd[5481]: Starting flatpak document portal service...
Sep 24 06:51:43 host dbus-daemon[5532]: [session uid=396 pid=5532 pidfd=5] Activating via systemd: service name='org.freedesktop.impl.portal.PermissionStore' unit='xdg-permission-store.service' requested by ':1.3' (uid=396 pid=5540 comm="/usr/libexec/xdg-document-portal")
Sep 24 06:51:43 host systemd[5481]: Starting sandboxed app permission store...

I've tried following env vars:

export GTK_USE_PORTAL=0
export GDK_DEBUG=no-portals
export GIO_USE_PORTALS=0

but none of em do the trick. FWIW export GTK_A11Y=none disables the accessibility bus just fine.

What is the correct way to get rid of portals for greeter user?