I used nonadhesive shelf liner for the longest time - for solid substrate I like it best. If you are not interested in tile though, maybe that won't work either? I think some folks have tried out the zoomed excavator clay - it's a water soluble material that dried hard but looks like sand or dirt. There is also a desert version of reptile carpet - a rubberized mat with stones and sand adhered to it.
If you want to use a loose substrate - look into a sand/soil mix, or a bioactive system. There is a thread about it on the "back room" board, (you can join via your us are controls). Of course - loose substrates will always have more risk than solid, and the soil is a bit more involved to maintain. I switched to soil recently... I'm not sure how much I like it or not yet.
Plain Coco coir holds moisture, so unless you take precautions you can have humidity problems - when it's dry it is very light, and that contributes to the mess. I've gotten slivers from mine (Ecoearth) - just something to think about. I'm not sure what "dry" substrate would be suitable. Anything lacking moisture will have similar problems as sand - dust and crud to get stuck in noses or breathed in.