The C# impl is still early and I think what will end up happening is that a lot of the boilerplate will end up being owned by source generators in the long term. C# team has a habit of "make it work, make it better". Whatever v1 gets released is some base capability that v2+ will end up making more terse. I'm happy and OK with that; I'd rather have ugly unions than no unions (yes, I already use OneOf)
Ah Source Generators, after all these years still badly documented, when searching you most likely will find the original implemenation meanwhile deprecated, have poor tooling with string concatenation, and only have a few great blog posts from .NET MVPs to rely on.