Ubuntu 18.04: how to display hostname on login screen?

[Jacques Beigbeder]

Hello Ubuntu experts,
 
Since I have 50+ Ubuntu in 2 rooms, I want to display the hostname
on the login screen. 16.04 did this (upper left corner).

How to get this with 18.04?
Some trick in /usr/share/gnome-shell/theme/ubuntu.css?

Thanks,

--
Jacques Beigbeder                    |  Jacques.Beigbeder at ens.fr
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