Armory 3D might be worth looking into because it uses Kha backend which is super portable. Tho I’ve not played with this yet so I can’t give you any tips but you could ask at https://forums.armory3d.org/
If you can get haxe code executing OpenGL draw calls on their own (or Metal for that matter) you’re in a good place – we can setup a native context using whatever build tools apple release and then call into haxe each frame to do the actual drawing (I’ve released a few projects using this approach). This is same approach we took for the WatchOS project just with an added graphics context (Missing hxcpp.h in cpp compilation - #8 by Lelelo1)
For OpenGL and Apple: Apple is of course deprecating OpenGL but I’ve had good success using MetalANGLE to translate OpenGL calls to Metal
I’m very exited for whatever Apple releases here!