Qt5 is really underused for how good it is. It's a really good platform for making native apps and it even has bindings for many different languages.
And since it can be used for IOS&Android apps it's a great competitor to React Native. It is reactive and declarative like React but with way less boilerplate and everything is so much easier to do, and it supports more platforms. The only thing React Native has on it is native looking widgets for IOS, but if you plan on using your own design anyway, that's not a problem.
You get the productivity of a modern reactive framework with the completeness of Qt. It has things like a GUI builder that modifies and generates code for you, and the code it outputs is close to what a human would write, so you aren't locked into it.