I’m trying to apply a voronoi texture from shader nodes and it only works in Cycles, in Blender site is not specified that it wouldn’t work in Eevee and I have an example here where it is working in this render engine: Fake Anime water blender 2.8 Tutorial
What’s to do?
It works fine here. Perhaps you shoudl specify what exactly doesn’t work and post an image to describe how it seems broken.
The voronoi Texture was changed in Blender 2.81 and works differently now. You’d have to figure out how the settings in your tutorial can be achieved with the new node. It is probably possible but will probably take some time.