It sounds like the issue you're experiencing with grey or glitchy outlines in Unity is related to the mismatch between your export and import settings regarding alpha handling. When exporting from Spine, you have the option to use either "Premultiply Alpha" or "Straight Alpha." If you choose "Premultiply Alpha," you must ensure that Unity is set up to handle premultiplied alpha textures. This involves enabling premultiplied alpha in the material settings in Unity. If you switch to "Straight Alpha," you should enable the "Bleed" option during export and ensure that Unity's texture importer settings are configured for straight alpha.
To resolve your issue, you should match the export settings from Spine with the import settings in Unity. If you are using premultiplied alpha, make sure that Unity's material settings are also set to handle premultiplied alpha. If you are using straight alpha, ensure that the "Bleed" option is enabled during export and that Unity's texture importer is set for straight alpha. This should help eliminate the grey or glitchy outlines without causing other issues like screen effects.
