Thanks for reaching out to us.

For now we do not plan to support HDRP in the near future, we just support URP 2D/3D and LWRP of the scriptable render pipelines.

The reason is that we did not see any benefit of using HDRP pipeline with 2D assets yet. Could you please let us know why you would like to use HDRP with Spine, or with 2D in general?

Thanks for getting back to us, I see your point! At least it says on this Unity forum thread that realtime point light shadows for URP are being worked on, so perhaps this will be supported in the near future in URP as well.

Hi, we're using HDRP as we mix 3D environments with sprites. I see on the roadmap that hdrp shaders are not planned, so if we use Spine we will likely need to convert the URP shaders that are provided. Are there any gotchas that you may be aware of, that can help us in our conversion?

You can see the most important points listed here on the spine-unity page, especially the subsection Caveats when using non-Spine shaders or visual shader editors:
spine-unity Runtime Documentation: Shader Graph
The most important decision will be to either exporting your atlas textures using Straight alpha workflow, unless you use additive blending at Slots frequently, in which case your HDRP (or shadergraph) should be configured to use additive blending and perform the PMA vertex color alpha multiplication there (that's described in the spine-unity documentation page).

In general any non-Spine shaders work with Spine skeleton components out of the box when using straight alpha export. You will just need to add some code in those shaders if you want to utilize special features such as single-pass additive blending (via PMA Vertex Colors, which need to be processed in the shader) and special Spine features such as the tint-black feature (which also works by passing additional data per vertex, which needs to be processed in your shader).

If you need further help down the line, feel free to post your questions here on the forum, as it will be difficult to foresee all potential scenarios at the beginning.

This is Brilliant, thank you so much.

You're very welcome, very glad it helped.