Not the countries I expected in Europe. I have traveled a lot in Spain/France/Italy and seen very few in hotels or private homes/AirBnBs. Let’s change the question: In which countries would it be seen as odd to not have one, rather than them being “not uncommon” as I’d assume this map is? Is that only in Asia these days?

That’s strange, because Italy has a law in place for which is mandatory to install a bidet in at least one bathroom in the house. “Health Ministry Decree 07/05/1975 Art. 7: For each accommodation, at least one bathroom must be equipped with the following sanitary facilities: toilet, bidet, bathtub or shower, sink.“ (https://www.indicenormativa.it/sites/default/files/Decreto%2...)

Weird. Maybe hotels are exempted from that?

I am from Italy and I've never seen a house or a hotel there not having one. We have been used to use it since we are young and when speaking to other Italians abroad, the talk about "how can these people live without a bidet?" comes out a lot.

Must be tough for Italians to travel across Europe and feel like savages when using bathrooms on holidays? A bit like when I use the “hole in the ground” model of toilet in some countries I guess.