"if you have proper architecture (which you should have anyway), you can test everything except for actual views" Totally agree. "I'd rather focus on making most of a project shared" Also agree. You need a model with smooth interop, which in the case of KMPP means actual/expect, and on the iOS side creating frameworks. On Android, it's 100% native, so not an issue. RN, Xamarin, Flutter, whatever, all suffer from foreign interop pain, and in general its significant. The Airbnb/RN situation has turned into a weird rorschach test for RN, as pretty much everybody tries to use that to prove their point (for and against), but a big issue was related to this other 3rd environment that required a lot of upkeep.