I am not sure, how I got it enabled like this, but here is a way to replay the problem.
General Discussions as whole group was selected, which you cannot achieve manually - but by following this link: https://en.delphipraxis.net/?forumId=8
When in fluid view, you will notice (which I did not), that the group heading is slighty highlighted. Selecting any group, will show its contents, but removing that check mark again, will bring you back to my previous problem...
Know, clicking on the "General Discussion" group header, will unselect that group and bring all back to its original state.
I do not know, how I got into the problem in the first place, I just found a way to replay it... Anyways, all back to normal for me.