A big reason I couldn't stand any gecko forums was the topic of substrate use. I still, several years later, have all my geckos (right now just African fat-taileds) in a fully planted tank with organic soil, sand, or some combination of the two. And still, if I share a photo of my tank on the Repticon page on FB, for example, the first 17 comments are "oh no, substrate!" And I just don't get it lol. People forget animals come from places that have an abundance of substrate and debris and that hasn't stopped them from getting this far, thousands or millions of years later.
Obviously you have to be smart. Don't have wood chips or a floor lined in pebbles, those are never going to pass though a GI tract. But something that is small, particulate, and contains no fertilizers/pesticides/other poisons it something a normal, well-hydrated animal can easily pass.
I've had several vets confirm this, and they agree that a vast majority of impaction cases (even with sand or soil) stem from poor husbandry in general. They say that any time they have an impaction case it's from an animal that doesn't have access to enough water, the temperatures/cage are all wrong, and it's in poor condition to start with. Not all, obviously, but almost.