This can only be set in the desktop app (not on the mobile version), but it is by default set to username.
As I understand it, changing the setting in the system console, changes the default for all users (and also for the mobile versions as these cannot make this change on their own).
So while I can change this setting for me in the desktop app (or web app), what I am trying to do is to make the change for all users so the new default is not username.
And what I see is that even though I make the change in the system console, the config.json setting is not changed which leads me to believe that there is a problem somewhere…