I think React Native is also a contender, now with Windows and macOS support coming online. Yes, the "UI Framework" story still needs some work and it's obvious

I think React Native is also a contender, now with Windows and macOS support coming online. Yes, the "UI Framework" story still needs some work and it's obviously nowhere near the web, but otherwise it's a nice middle choice where you get a lot of the perf benefits and "native UX" look and feel, while still being able to leverage a lot of webdev skills like JavaScript and Flex.