Well as a company, we still use Flex for Android and iOS apps (android tv and tvOS included) and we have at least 1 for windows 10 and macOS. If you are comfortable with flex you can build almost anything in a few hours.
I had issues when it comes to more advanced apps for Android but in most cases you can overcome them. If you want to be 100% future proof I would suggest Flutter or React Native for cross-platform or go native! You can't never go wrong with native!. That being said the community is awesome and I don't thing that there is another cross-platform technology that compiles iOS apps in windows! -- Sent from: http://apache-flex-users.2333346.n4.nabble.com/
