Per [1], PWAs on webkit lacks push notifications, full-screen display, hardware acceleration, web bluetooth as major headline features needed, which Firefox on mobile appears to generally support per a 5-second glance (I didn't see web bluetooth, but the rest I did) [2].
That wikipedia page has a support table saying IOS supports PWAs as YES and Firefox as NO is odd considering Apple requires Mozilla to ship a crippled form of safari on IOS, if Firefox could ship their own true application, I suspect they would have better PWA support as a differentiator with Safari.
