I never understood that. Qt is C++. The only valid reason to use C++ is "not having a choice" (which happens to me, too). But if you write a mobile app, I find it extremely weird to choose C++ instead of a modern language.

Disclaimer: I have seen teams writing mobile apps in Qt, and it was systematically a lot slower to develop, with a lot of pain, and resulting in worse apps. Even if you only have C++ devs, I would argue that it may be worth giving them the time to learn a modern language and write the mobile app with it.