I suspect HongMeng will be very close to Android.

Is that much worse than supporting Mac OS, Linux and Windows on the desktop?

Cross platform SDKs are more mature on the desktop than on mobile, so doing the same on the desktop should be easier.

The more mobile OSs we get the more likely we will develop better cross platform support.

Which is also good to break the iOS/Android duopoly.

Microsoft already tried to do that with their Windows Phone operating systems, and they weren't particularly successful even with some pretty big efforts on their part.

They went as far as making it possible to run android binaries on Windows Phone (Project Astoria). They also made Visual Studio able to compile Objective-C code so it could make iOS codebases into apps for Windows Phone (Windows Bridge for iOS)

Some programs even support BSD as well

I imagine the tooling will just get better to the point where its like electron, you don't even think about what OS the user is running.

I look forward to a future where we can enjoy Electron-like efficiency on our battery and storage constrained devices.

I must assume you are sarcastic, unless perhaps you are talking about efficiency on an a different scale than the one I'm thinking of (which would be battery life and storage). Can you elaborate?

There is an easy solution: don't support Hongmeng. It's not like your IP will be respected anyway.