Sadly, Firefox has abysmal support for PWAs on both mobile and desktop. I love Mozilla and Firefox -- and I still use it as my primary development browser -- but at this point Firefox is functionally worse than Chrome, Edge, and Safari on most axes.
To be real, only Safari actually matters as alternative to Chrome.
Firefox is also my main browser, but that doesn't change the fact that its 3% market share has made it optional for project delivery acceptance testing.
For me it's sad how I have to use Edge (because it's already included in Windows) due to many pages don't suporting Firefox. Google has made all they could to make both people and developers to use Chrome and Chrome-based browsers.