I trained my dog on a litter box. She only pees in it. I'm very glad I did.

However, I'm fortunate enough to have a basement I could put it in where it's out of sight.

That's a thing and people.do, especially apartment dwellers. Dogs learn it quick too.

It's just no one would have an animal shit in a box in the house unless they absolutely had to.

Oh...

1. I don't train my dog to use a litter box because I don't want to clean out a shit box.
2. You probably could train one to use the toilet, but you'd probably need to make some modifications to make it possible. I don't see most breeds of dogs being able to balance themselves quite well enough for things to work 😅

Cats leap and perch with more ease than dogs so you'd need a contraption that might get in your way.

Its a good idea, but from my understanding, you still have to take dogs on daily walks. Maybe not first thing in the morning, but at least once a day or so