Not sure where to ask this but is it still the case that prisma does not support interfaces nor union types?

That is correct, but there is an RFC on a plan to rectify that: https://github.com/prisma/prisma/issues/3408

What do you think of this workaround? https://itnext.io/graphql-interfaces-and-union-types-with-prisma-and-yoga-7224f9e1d9ad?gi=c91a575891d

Well, it’s not easy, but we do it… sort of. I’m mostly waiting for them to implement the above data model directives. As for the article, I’ll have to check that out