Any non-digital one would be fine. Your boss can tell what feels comfortable. I’ve never heard of braille being on buttons but I use clear braille tape to label all buttons on my stove.

Make sure it has a knife rack. It's a little tray on the very top that pulls out. You put anything sharp up there, that way they can't cut themselves.

Something that isn’t digital would work. Tactile buttons would be the best that way he could identify them by feel but he could use bump dots or braille labels to differentiate between buttons and settings. Any other type of sticker with a textured surface would work as long as he remembers what they indicate on the dish washer.

I am going to go against the grain and suggest an LG. The buttons could easily be memorized or you could make use of Braille tape or colored tape (depending on level of impairment). I’m the buttons make noise when pressed and it plays a tune when it is done.

Many also include a little 3rd drawer at the very top which is great for cutlery.