When it is dry, that is, ready to be covered. Of course, this cannot be said in general terms, as every house or screed dries differently. In the screed, there should be a hole in every room where the residual moisture can be measured.
Which screed? Flowing screed or cement screed? When was the screed laid/poured? Since when do you ventilate, how do you ventilate, and is the heating-up program already running?
Why do you ask, have you already given notice? :p
Ceiling joints or plasterboard filling? well then cheers! Can you even do that, have you done it before? Everyone can paint, but not everyone can fill!
Filling always works. Painting when the wall looks dry. Don’t forget the primer. Klick vinyl if the floor is nice light grey. With the click method it’s not as critical as glued. Glued must have a really dry substrate.