Under Web Proxy & Filter in the current NethServer version 7.7.1908 no users and groups can be selected under the new NethServer UI (Cockpit) when creating profiles. Only computers appear during the input.
Under the old NethServer UI (Nethgui) the selection of users and groups works as usual without problems.
Existing profiles are displayed under Cockpit and can also be edited.
The who field can be populated with user names only if the system has a configured account provider and the proxy mode is set to authenticated.
This a design choice, because if other conditions the profile couldn’t be applied.
Sorry for the late reply, I had no access to my NethServer installations during the weekend. Okay, that was the trick. I hadn’t set the proxy to authenticate. But now I can’t share any more computers.