Unfortunate, that this is still not available.
The builtin shaders are an invaluable learning reference and a great starting point for creating your own shader.
Update for everyone that has liked this post or replied here: It seems this is fixed.
If you open a unity version page in the download archive, there is now the point “Other installs → Shaders”.
Thanks Unity for fixing it. I would have appreciated some communication about it, but maybe you didn’t see this post.
And the important thing is that it’s working now