Comment 10 for bug 1759043

Editing /etc/gdm3/greeter.dconf-defaults, as Jeremy suggested, works for me too. However, also the instruction in system-admin-guide works fine for me, so making an Ubuntu specific variant of that page seems not to be motivated. Possibly there is room for improvements of the upstream page.

@Fábio: Before suggesting anything, it would be valuable to know why it failed for you. For instance, did you successfully create the dconf database? For me it looks like this:

$ ls -l /etc/dconf/db/gdm
-rw-r--r-- 1 root root 240 mar 29 23:45 /etc/dconf/db/gdm