Hey,
Make sure on your material settings that the Unity UI default shader has its mask mode set to "Outside". I accidentally shipped a build where that value was set to "Inside" which doesn't render text.
Try not importing the legacy shaders - those all used surface functions, and all the new shaders use fragment functions. These will be excluded from the next 1.x patch.
Finally, try right-clicking on the .cginc files in the "Shaders" folder, and click "Reimport".
Please let me know if any of these work! That last one is strange, but Unity doesn't automatically recompile .cginc files when they change, and I just realized that they new .cginc files wouldn't line up with the new shaders after an update. Hopefully that's the one that fixes this?