Hi Raphael,
If you are just starting out with Haxe I wonder whether Sandy3D is the best choice for 3D graphics. You may have noticed the repository has not been updated for 10 years.
Might I suggest exploring the following options to use with Haxe:
Away3D - it features tight integration with OpenFL. It lacks import/display support for glTF and does not support AR/VR. Cross platform. I use this.
Heaps3D - In active development and often used for game development. It lacks import/display support for glTF and does not support AR/VR. Cross platform.
Three.js - Only HTML5/Javascript support. It is more complex to set up with Haxe and externs but is very actively developed and has support for glTF, AR, VR. I use this.
Armory3D - Full game engine designed to integrate with Blender. Uses Haxe and Kha. Cross platform.
I should mention that BabylonJS is a capable alternative to Three.js in JavaScript and they both support gaussian splatting, which is an important technology these days. I’ve not tried it.