[unkown-unknowns]

I'd not heard of PWA before. After reading the OP I did an additional search on Google. Found a course on udemy that claims to be on sale.

https://www.udemy.com/progressive-web-app-pwa-the-complete-g...

I've seen three of the videos in it so far. Seems like an ok course for the ~25 USD I paid for it.