Well fun. I have an OpaquePointer and UnsafeMutablePointer from a system interface that I have to pass around/use, and I've discovered pointer types are non-sendable in Swift Concurrency. So it looks like I'm going to have to do a major redesign in order to get to Swift 6 by coming up with some sort of actor-based framework.
The interesting thing is I already can envision some major code structure improvements due to this, assuming I can get it all to work.