The Windows build doesn't fail (it uses a docker image with pre-installed deps), but devhelp does not configure, possibly because that image doesn't have the requisite dependencies.
The Docker image is not really relevant here, it only has some dependencies as some sort of cache. The workflow definition in the project is the authority for installing dependecies.
Maybe because of webkit, @eht16 is there a even a webkit for windows? Webhelper doesn't configure on windows either.
There is no more WebkitGTK for Windows: ***@***.***/thread/4DEVGI2ICZX7F7GE6FLSNNQF3Q6I2OP7/
The link in the post is broken, the correct one should be https://github.com/MSYS2/MINGW-packages/issues/4318.
So, the devhelp plugin won't be available on Windows at all.