I use one. I have an apple orchard. I dehydrated hundreds of pounds of apple slices. They are wonderful! Use an acid in the water that you slice the apples into. Lemon juice or Fruit Fresh
I dehydrated potatoes, carrots, sweet potatoes, celery. Those need to be blanched after slicing, so they don’t brown. I also dehydrated bags of frozen veggies. This way, they don’t require refrigeration, they last forever and they weigh little and don’t take up much space.
Did you blanch the frozen veggies before dehydrating them?