Hello there,
I am an experienced programmer. I can do C/C++/Rust/assembly/Ruby/Perl/Python/ etc.. The language itself is not a barrier.
The barrier to me is that I have never coded a single web or android application. I guess it must be surprising but I am more of a low-level programmer in my job (I develop a compiler backend) and I never really had the opportunity or idea to work on an app.
What would be a good starting point for making an android application?
A quick search got me this: https://google-developer-training.github.io/android-developer-fundamentals-course-concepts-v2/unit-1-get-started/lesson-1-build-your-first-app/1-1-c-your-first-android-app/1-1-c-your-first-android-app.html
Would it be a good starting point?
Side note: my app will not have to interact with any service. If I were to code it as a command-line program, it would not take me more than a day or two. The actual app would involve (for now) no more than a text field, a button, some logic attached to it - the hard part for me being to choose a framework to build it, "upload it" to my phone and use it.
That doesn't seem like a bad start to me, but I haven't read it thoroughly. I also recommend checking out the official Android Studio beginner's guide: https://developer.android.com/get-started/overview
Alternatively, you can use wrappers like Flutter, React Native, or the Ionic framework if you think you might want cross-platform or web capability later, though that adds a lot of overhead that isn't always the best choice.