Note that PWA is a concept, not a specific set of features or APIs. This makes a lot of this discussion confusing and mostly meaningless. Furthermore this bug is about a browser feature. The similar "PWA" API here would be https://developer.mozilla.org/en-US/docs/Web/Manifest/displa... which is supported by Firefox for Android so it isn't like Firefox won't support "PWA" as a whole and will reject all of the related APIs.
And remember that PWA is Progressive Web Application. The P is from Progressive Enhancement[1]. This means that missing an API or two doesn't mean that your browser doesn't support PWAs. It just means that some PWAs will have less functions or give a less "app-like" experience.
And remember that PWA is Progressive Web Application. The P is from Progressive Enhancement[1]. This means that missing an API or two doesn't mean that your browser doesn't support PWAs. It just means that some PWAs will have less functions or give a less "app-like" experience.
[1] https://en.wikipedia.org/wiki/Progressive_enhancement
TL;DR that bug is mostly meaningless, the underlying APIs are what matter.