@rffaguiar We have finally added support for Tint Black functionality at all Spine URP shaders (2D and 3D shaders) and at all standard pipeline Spine/Sprite shaders. This feature can be enabled via the Tint Black material parameter in the Inspector. Note: The URP Sprite shaders provided in the Spine URP Shaders extension UPM package require the latest version of the spine-unity runtime (package version 4.1.12, 2023-05-31 or newer) to display the added material parameters in the Inspector GUI.

The respective commits have been pushed to both the 4.1 and 4.2-beta branches.
New 4.1 and 4.2-beta spine-unity unitypackages and Spine URP shaders UPM packages are available for download here as usual:
https://esotericsoftware.com/spine-unity-download

Sorry that this feature has been delayed for such a long time!