Comment # 11 on bug 1050953 from Freek de Kruijf

(In reply to Fabian Vogt from comment #10)
> (In reply to Dominique Leuenberger from comment #9)
> > ListCachedUsers lists the users
> > 
> > > gdbus call --system --dest org.freedesktop.Accounts --object-path /org/freedesktop/Accounts --method org.freedesktop.Accounts.ListCachedUsers
> 
> It doesn't list *all* users here, which is the issue. It only lists the
> users that "CacheUser" has been called for, with no option (apparent to me)
> to list all available usernames.

Did the following:
freek@eiktum:~> gdbus call --system --dest org.freedesktop.Accounts
--object-path /org/freedesktop/Accounts --method
org.freedesktop.Accounts.ListCachedUsers
(@ao [],)
freek@eiktum:~>

freek@eiktum:~> qdbus-qt5 --system --literal org.freedesktop.Accounts
/org/freedesktop/Accounts org.freedesktop.Accounts.CacheUser
Error: org.freedesktop.DBus.Error.InvalidArgs
Berichttype ���()��� komt niet overeen met verwachte type ���(s)���
freek@eiktum:~>

freek@eiktum:~> qdbus-qt5 --system --literal org.freedesktop.Accounts
/org/freedesktop/Accounts org.freedesktop.Accounts.CacheUser $USER
[ObjectPath: /org/freedesktop/Accounts/User1000]
freek@eiktum:~>

Remark: the above prompts for the root password.

freek@eiktum:~> gdbus call --system --dest org.freedesktop.Accounts
--object-path /org/freedesktop/Accounts --method
org.freedesktop.Accounts.ListCachedUsers
([objectpath '/org/freedesktop/Accounts/User1000'],)
freek@eiktum:~>

So apparently the users need to be entered first before systemsetings5 can do
something with these users