What options are there - apart from Raufaser - for the Q2 substrate without extensive and above all expensive sanding and filling work?
Under that premise, besides tiles, only Gobelin would come to mind.
Seriously though. Even in old buildings, we simply painted directly over the plaster, so you can definitely see where, for example, a door was closed off or plaster was repaired – we find that beautiful. But I must also say that after a short time, you simply no longer pay attention to it.
In my opinion, this is one of those details that keep you awake at night during the construction phase and, depending on the outcome of your personal pondering, end up costing a lot of money, but afterwards no one cares anymore. There are furniture pieces in front of the wall, pictures, photos, posters, paintings, postcards, curtains, blinds (... Gobelins) on the wall, and anyway, a furnished house offers so many more eye-catchers than the structure of the wall surface.
And even if later some spot catches your eye so much that you get construction pain walking past, you can still beautify such a wall afterwards without having to move into a hotel for weeks. The easily five-figure amount you save by skipping sanding, filling, and wallpapering the entire place can be spent on much nicer things that have a much greater impact on living comfort (e.g., a whirlpool ).
I know, baby-bottom-smooth surfaces, perfect 90° angles, minimum joints, clear lines – clean aesthetics are "in." But it (not just the wallet) feels incredibly good to break free from that and reflect a little of your own imperfection in your home.