There probably are some dogs about who've been taught to use the toilet.
I stayed with friends whose cat was trained to pee on their toilet in the master bedroom.
One evening, when I knew my friends were gone and I was alone in the house (or supposed to be), I suddenly heard very loud peeing from the master bedroom.
My heart thumped, thinking it was an intruder.
It was the cat.
They did not train her to flush.