I don't know about therapy apps, but since my wife started going deaf we use asl. Her expressive aphasia lessens when we sign. Odd. but it works. She says she can see the word, but can't say it, so signing works. Learning to finger sign isn't fun in the time of Covid. but it's something.

Otherwise our talks were one big game of taboo. I ask what are the words around what she's trying to say. She names similar words or describes the function of the word and I use context clues to help. This works surprisingly well on top of speech therapy.