I feel like this is a use-case which sounds a lot better on paper than it actually is. Mobile apps in my experience tend to be shaped quite heavily by the syst

I feel like this is a use-case which sounds a lot better on paper than it actually is. Mobile apps in my experience tend to be shaped quite heavily by the system API and UI frameworks they are built on top of. When you talk about the "common part", usually this is like the networking layer and models maybe, which tends to be very simple and takes like a half hour to write in the first place. Even if there is a little duplicate work, it's still better to have the whole app implemented in the native language and frameworks, rather than having some odd bits which don't work with the same tooling for example and are harder to debug.