In May this year this was already a discussion point that the User and Groups menu isn’t visible after the initial installation. I will not start the discussion again but the documentation isn’t consistent.
In the documentation is written:
If the directory module is installed, and the admin user has been enabled, you can use it to access
the web interface with same privileges as root user. See Admin account.
Sorry, I can’t find a Directory Module.
I propose a list of the modules if they are installed which will create the User and Groups menu to make it clear. I don’t know which this is otherwise I would add it.