All of these API surfaces are pretty large- what is a good way to get a feel for what they do/don't offer? In particular, what are you referring to in .NET Core that you wouldn't want in Framework?
.Net Core supports P/Invoke on Linux and macOS, you aren't going to be using a library that provides bindings for libsystemd.so or whatever on Windows - this is probably one of the most prominent examples. I know there's a handful of others, but I'm having a hard time finding a good article or any relevant documentation on it.