Are any greases not dielectric, or are some labeled as such because that is
the only quality they have , i.e., no lubricating quality ?

I have used a dielectric grease where it was suggested to me, to ensure a
good electrical connection for a ground, or so I thought.

So when I secure a zinc to my saildrive should the bolts be coated with
dielectric grease, or any grease, or no grease ?