This Spine/RGBA shader is not an official shader. You can always check this list here on the documentation pages:
spine-unity Runtime Documentation: Shaders
sunnyboy76 написав If not, are there any shader supporting alpha channel in the official built-in shaders?
All shaders support alpha channel, it would not make any sense not to.
If you are having problems with the alpha channel, you most likely did not export and setup the textures accordingly (straight alpha vs PMA) as described here:
spine-unity Runtime Documentation: Advanced Premultiplied vs Straight Alpha Export
If you see pink materials, you are most likely using Unity standard shading pipeline shaders in a project using Universal Rendering Pipeline (URP). For the respective Spine URP shaders, please see this extension UPM package:
spine-unity Runtime Documentation: URP Shaders Extension UPM Package
