Ideas for a low-maintenance house

It might be a bit of a stretch, but I would also recommend "Magic Cleaning" by Marie Kondo on the topic. You can try it for free as a series on Netflix, but it’s more about families decluttering. The book also has a lot of practical advice for people with normal households. It’s not specifically about cleaning, but as Shiny already said -> having fewer possessions makes life nicer and also makes it easier to keep the place clean. One of her most basic rules is to have as much as possible behind doors and fronts. The less is standing around on surfaces, the easier and faster you can clean them. It already starts with the kitchen countertop. It makes a big difference whether I have to go over it once with a hot cloth and dish soap after cooking, or if I have to lift 30 objects, set them aside briefly, and put them back again.

There is a quite nice, well-known book on this: "Simplify your life" and I believe also a website with this keyword, podcast, etc. Now that I am reminded of it here, I want to read it.

not stairs but a ramp, so that the robots can clean both floors.

I don't know if your comment was meant seriously or not, but I find it brilliant. Could you please tell me why this is so rarely or never implemented in houses? Going up a ramp is not more exhausting than climbing stairs, or am I mistaken? Besides, everything could then always be rolled up and down nicely without having to carry things.

or am I mistaken?

You are mistaken!

My leg-bound father-in-law might possibly be able to walk up a ramp. Downhill he could not support his weight with the still somewhat functioning leg and would inevitably fall. He can manage stairs – step by step, though.

You can also simply get a robot vacuum for each floor. You probably have the money for that, and you don’t have to carry the device back and forth all the time.