Not that popular yet, but the Newspeak programming language runs entirely as a PWA, up to the IDE. Makes it really easy to set up. See https://github.com/newspeaklanguage/newspeak and https://groups.google.com/g/newspeaklanguage/c/s7c74c4QVvM

I think the Starbucks PWA is pretty good example from an implementation standpoint.

Youtube is probably one of the most popular