There are some apple-pear hybrids that produce fruit. Development work seems ongoing in Germany. Unfortunately for me as (mostly) an English speaker, most of the papers describing it are in German. Here's a summary of an abstract in English, though: https://agris.fao.org/agris-search/search.do?recordID=US2014.... If you search for the primary author plus some keywords (Thilo Fischer Apfel Birne) you can find articles that give more details.

I'm guessing the Sorbopyrus you are describing is the Shipova: https://en.wikipedia.org/wiki/Shipova. It's a surprisingly old hybrid. I've got one growing, but haven't gotten any fruit yet. Have you eaten it?

I have never eaten it, but it's at the top of my list of trees to grow once I have enough space for it.

Never heard of it so for others https://en.wikipedia.org/wiki/Shipova

Can't cross with an apple but can with a whitebeam, I wouldn't have believed it. Amazing, thanks.