If it's dbus-activated, you might need, although the touch session doesn't do that, and works regardless...
gdbus call --session --dest org.freedesktop.DBus --object-path /org/freedesktop/DBus --method org.freedesktop.DBus.UpdateActivationEnvironment "@a{ss} {'QT_QPA_PLATFORM': 'ubuntumirclient'}"
If it's dbus-activated, you might need, although the touch session doesn't do that, and works regardless...
gdbus call --session --dest org.freedesktop .DBus --object-path /org/freedeskto p/DBus --method org.freedesktop .DBus.UpdateAct ivationEnvironm ent "@a{ss} {'QT_QPA_PLATFORM': 'ubuntumirclient'}"