From opensource.com: A Drupal developer’s guide to Progressive Web Apps

Here is an outlined approach to PWA implementation for a Drupal site, but other options are certainly available with similar designs.

Source: A Drupal developer’s guide to Progressive Web Apps

Progressive Web App plugin for WordPress under development with eye toward core integration

WordPress feature plugin to bring Progressive Web App (PWA) capabilities to Core…
The plugin exposes the web app manifest via the REST API at /wp-json/app/v1/web-manifest

HTTPS is a prerequisite for progressive web apps. A service worker is only able to be installed on sites that are served as HTTPS. For this reason core’s support for HTTPS needs to be further improved, continuing the great progress made over the past few years.

Source: PWA :: WordPress.org

This is an interesting development. If successful including this functionality into WP Core would turn every WordPress site into an app. That would be fun.