Thanks for reporting!
It seems as if the Lightweight Render Pipeline/Lit shader uses Custom Render Queue = 3050 when transparent, so it's drawn a bit after the other shaders. It draws correctly when I set the Priority parameter of the transparent material to +50, resulting in the same render queue value of 3000. I will do some more investigations whether it is safe to increase it to 3050 as well, and will then release a bugfix soon.
You can find a new isue ticket here:
https://github.com/EsotericSoftware/spine-runtimes/issues/1568
I will let you know once the issue has been resolved.
Thanks again.
Sorry for the long delay. Actually this can only be resolved by manually setting the render queue at the materials, neither render queue default values 3000 nor 3050 will work for all cases.
See related issue ticket [unity] Sprite shader render queue property too limited ยท #1737, and commit 996cbea which adds better render queue control to all Spine Sprite shaders (including LWRP and URP).