Just to confirm the terminology commonly used in mobile app development:
- Native apps - Written in compiled languages compatible with the target platform, uses platform-specific APIs.
- Hybrid apps - A "native" framework that loads web pages in a WebView (even if they are served from device storage) and has access to platform-specific APIs if the framework supports them.
- Progressive Web Apps - Written exclusively for the web, a PWA may only use web APIs. Platforms may allow users to add PWAs to app select screens, specify an image to use for a splash screen while loading, use the PWA offline, and hide the address bar to mock a fully-native experience.
With that out of the way, Drupal lists a few resources to get started with mobile development in their documentation. Unfortunately it's quite outdated, as PhoneGap has been discontinued and all the other resources show their age.
The sections headed Native apps for iPhone... and Native apps for Android appear to only include examples using Drupal as a RESTful API, so you are creating a whole app UX/UI from scratch on each platform, not with Drupal.
Though PhoneGap doesn't exist anymore, Apache Cordova lives on as a hybrid app framework and is a good first start for someone not yet comfortable with native frameworks. It is compatible with Drupal or any other CMS.
Finally, here's info on Drupal PWAs.