What are the possibilities of an Android app. Qt says it works on Android but not sure. A C++ dev here. How much of an effort would it be to port it to Android or do you see any blockers?
If you are confortable doing the whole UI in QML and eventually creating your own JNI/Java wrappers for APIs not yet wrapped in Qt, it is doable.
The Qt Widgets are focused on desktop workloads, so they aren't much usable, you might even get a desktop looking dialog poping up.
If you really want to go with native Android UI route, then there isn't much help Qt can provide here.
Major blocker is that after all these years Google still doesn't provide any kind of tooling to improve JNI workflows, we only get the basic java -> header file generation tooling, e.g. javah.
But eventually you have to rethink the user interaction and also deal a bit with layout changes for portray/landscape, manifest, permissions and stuff and stuff. Depends on your app how much work is here.
If mobile stuff gets complicated and you need to do a lot of custom things with device hardware maybe Felgo is worth looking at. It's a Framework for mobile development build on top of Qt/QML