Migrate Appcelerator Titanium mobile app to new technology

I have a mobile app that is currently built using Appcelerator Titanium. We are maintaining it using the now open source SDK after Axway discontinued the product. Our current developer has been with us for the entire life of the application which is now 12 years old. It is a small B2B application currently built only for Android and is not on any app store. Unfortunately our current developer does not have the time to continue working on our application. We are now looking to migrate the application to a more modern framework such as React or Flutter. If we can find the right person we would also be open to maintaining the application in Appcelerator but we have not had any luck finding a developer still using that framework. The application contains a lot of math, custom settings, and configurations in order to be flexible for our users. As such, we are looking for an extremely detailed oriented developer with very good English and understanding of business. Our app is used by hundreds of technicians that rely on it to produce accurate results. If you are selected in the top 3 proposals we will allow you to review the source code before making any commitment to the project.