Thanks Noel!

I started from here
https://docs.moodle.org/dev/Moodle_Mobile_custom_apps

which has a link to this page to set up the environment
https://docs.moodle.org/dev/Setting_up_your_development_environment_for_Moodle_Mobile_2

And in that page it says to use the integration branch...
https://docs.moodle.org/dev/Setting_up_your_development_environment_for_Moodle_Mobile_2#Clone_the_app_base_code

Actually, the branding I did was just changing the icons and splash screens in the /resources folder, a bit of SCSS changes, fixing the URL to login only to a specific site.
So maybe it's worth saying to clone the master branch to make a "production-ready" custom app.

Once I have the whole thing neatly working, I would like to share the steps I did to ease the process for other developers: I am writing down an .MD documento with the steps to follow on a "main" linux box (for android .aab bundle app) followed by a "migration" on a mac to create the iOS app.
Do you think it is worth?