Hello folks. I'm a backend guy, mostly using Python, Go, and the like. I've learned a bit of Rust and have enjoyed it for embedded.

With that background I'm curious if any mobile devs can give some feedback on the current state of cross-platform (Android, iOS, Web) for simple apps. What I currently have in mind, despite not owning a uterus, is a FOSS menstrual cycle tracker app, using encrypted local storage only (the regularity of this private information being sold by existing apps is very disturbing to me). This means that my reqs boil down to:

• UI/UX (I suspect this would require platform-specific code)
• Storage/DB subsystem (probably just use an encrypted sqlite)
• Optional extras
• Minimal third-party library usage to potential minimize data leaks as well as limiting possible vectors for ad injection

So, there's really not much to it complexity-wise. Any suggestions on framework or approaches for keeping the codebase DRY as possible (I would want to minimize required effort to update)?