I've tried looking specifically into the Apportable SDK during porting my app from iOS to Android. I've noticed several header files, including CALayer.h, in the .apportable/SDK directory. Are these .h files what is actually supported by Apportable? Because I've used the cornerRadius feature and it doesn't appear to work in Android although it should according to the .h. Thanks!
No, the .h files and their content needn't be an indication of what is supported by Apportable and what isn't.
Some functions are likely just declared but do nothing (stubs) in order for compilation to work even if a project uses unsupported features.
As (many of) the inner workings of Apportable are closed source, and supported features increase by the minute you should contact Apportable support if you need a definitive answer or more details.