I use a Nesco unit. Neevr tried bananas. Did apples once, but the wife made sure that they never made it into our storage! One short cut I will use and buying bulf frozzen vegs on sale and placing them right into the dehydrator they are cut blanched and ready to go!
I do bananas all the time. They brown, and you have really get them dry. It’s important to let it go until there is no softness. They may look spoiled but they are not.
I do tomatoes. My wife eats them before I can get them vac-packed.