It just turns out plants like more than 6" of dirt. Maybe I should've realized this already, but on the other hand, I learned this empirically with no support and second hand advice
I'm able to cook, I don't have a cursed non-green appendage, but gardening indoors is a skill I'm still working out
Or buy a Epipremnum aureum -- the houseplant that will laugh at your attempts to kill it.
The plant has a number of common names including golden pothos, Ceylon creeper,hunter's robe, ivy arum, silver vine, Solomon Islands ivy, and taro vine. It is also called devil's vine or devil's ivy because it is almost impossible to kill and it stays green even when kept in the dark.
Terrariums with small grow lights are a cheat code for these plants. If you keep it mega humid in there and let the water drain away from the roots so they don't rot, they go absolutely ham.