Is it possible to hide or disable the “Activities” icon for other users?
Why? What’s your goal? Does it bother a particular user? He shouldn’t make such a fuss. Tell him that you can still see what he’s doing in the logs, and only he won’t see he’s activities anymore, after you remove the icon.
To your actual question:
I want to see the activities as admin, I don’t want all users to see all activities in the cloud.
These are your options to hide the app from the menu.
You can also create an app group as an admin such as “Admin Only”, add Activity app to that group, and attempt to limit user access in that way.
Ok, i know it from other apps, but here i don’t find the possibility to add the app to a special group
Hmm. Seems it is not supported. I suppose this is because it is bundled as a core app. GDPR conformity: Limit to groups option · Issue #466 · nextcloud/activity · GitHub
Question: why limit access to activity app?
Users cannot see all activities in the cloud, but only those that involve their own resources or resources that have been shared with them. In other words, they can only see activity on things they have already access to anyways.