*For egg-free, substitute the egg white for 1/2 cup liquid from a can of cannellini/white kidney beans.
**If you are intolerant to vinegar, try substituting the vinegar with 3/4 teaspoon baking powder mixed into the dry mixture. It won't rise as high but works okay.
Substitute for Apple Fiber: Most likely, equal amounts of psyllium husk powder should work well as a substitute for the apple fiber/pectin.
https://glutenfreerecipebox.com/gluten-free-millet-chia-bread-udis-copycat-recipe-oven-or-machine/