You don't need a PWA to get push notification. There are providers like FCM, OneSignal etc.
What you will need is a NodeBB plugin. Kindly make a plugin request or ask quote for a custom plugin.
I've got two questions concerning notifications.
Is it possible to display more notifications in the "notification window"? This seems to be limited to 15? I know that I can see all on the /notifications page but it would be easier to just see more in the notification window.
Is there any possibility to display the category of the topics in the notification (either notification window or notification page)? Or should I put a topic for that in feature requests?
Thanks for your help.