I'll provide some objective information, as I probably know more about PWA's than anyone on here besides the Oxwall team.
PWA stands for Progressive Web App and allows a user to install your site as an "App" on their home screen directly from your site.
With PWA it bypasses being in the app stores and allows install directly from site. You may eventually be able to get a PWA in the App stores (Microsoft already does this supposedly.)
Now this isn't really an "App" in the traditional sense, as it isn't compiled or put into any package for download.
Instead, PWA's work through a set of specifications that you set in various files. Once you match all the specifications and requirements up to a certain percentage, the clients browser will prompt the user for install using the settings your site supplies. Most browsers now support most of all PWA functionality, except iOS/Safari is running behind. Apple has just recently enabled service worker and doesn't yet support Web Push Notifications.
All other major browsers are now fully or near enough to fully supporting PWA's with all features like Web Push, except Safari for security reasons regarding iOS.
A PWA consists of a few critical requirements that are mandatory:
1: Website Must Be HTTPS (SSL)
2: A Web Manifest:
https://www.w3.org/TR/appmanifest/
3: A Client Side Caching Service Worker (Caching Required for PWA):
https://developers.google.com/web/fundamentals/primers/service-workers/
4: App Icon at multiple various sizes and Theme / Background Color specified and included in Manifest
5: Site Loads Quickly Enough for 3G/4G
Here is a PWA Checklist and there is A LOT of info all over the internet.
https://developers.google.com/web/progressive-web-apps/checklist
Here are some resources:
https://caniuse.com/#feat=web-app-manifesthttps://whatwebcando.today/
https://love2dev.com/blog/what-browsers-support-service-workers/
https://superpwa.com/doc/progressive-web-apps-not-working/
You already know where to find the updated SkaDate PWA's, but here are my Oxwall PWA Plugins:
OxPWA Lite
OxPWA Basic
OxPWA Advanced
OxPWA Pro
OxHybrid (Hybrid App + PWA)
I found that the original SkaDate PWA wasn't a true PWA because it didn't automatically prompt for install, but I think that was to work around some limitations in IOS / Safari support.
They have updated their PWA with Google SW-Toolbox (Service Worker) and they DO now support install prompts on devices.
I use a very similar technique, using Google WorkBox Service Worker as an option along with various proprietary custom service workers I developed with some customizations for Push Notifications Subscriptions.
I am currently working on adding iOS to OxHybrid and creating a separate OxIOS plugin for Hybrid iOS App + PWA like OxAndroid does Hybrid Android App + PWA.
I have some proprietary idea's and code that I am about to test to get "web" push notifications working on iOS and if I am successful will be the first and only to be able to provide any sort of push notifications through iOS Service Workers!