My recent experience with NSwag was really bad... It could only handle the simplest of jsonschema. We were trying to connect with a typescript API that had heavy use of union and product types. Maybe the problem was just that C# doesn't support algebraic typings?
Yeah, the C++/Java/C# family of type systems have obvious holes in them. There are various hacks/implementations for them but since they're not in the core they're not really expected to be supported by random tools either.
Like mentioned, our regular pipe is C# producer (server) and TS consumer (client). Consuming services authored in Java,etc is usually not a problem either but the TS system definetly has a bunch of more cases that aren't easily mapped.