At the moment as a user of nomadsculpt I’ve personally been interested in some apps i could also add to my toolset, however as a hobbyist/beginner programmer i have no idea where you’d begin programming software for 3d art, much more a mobile software. How did it all begin, and where might a hobbyist start for specifically making 3d art apps?
Most languages can be used to write graphic applications. It’s more important to use a language you are comfortable with or one you are interested in learning. It’s also helps to have a large community using it. That will usually lead to some user-made libraries to speed up your development. Personally, I started writing a 3D app using Rust targeting WebAssembly. Rust has a steep learning curve, but WebAssembly is a good way to target all operating systems with a predictable way of working with a 2D/3D space.
Look up some tutorials on writing a 3D app in whatever language and you’ll likely be recommended a good starting point.