Ломающие новости, посоны:
We will very unlikely support multiple graphical logins of the same
user at the same time, in any default setup. Custom setups or setups
which declare that as supported will need to add their own logic to
make that possible.
Это цитата Кея Сиверса -- мейнтейнера udev и второго после ленички в разработке systemd/logind/journald.
