Alright well I have given up trying to use Firefox on Android for PWA. It's just unusable. Out of the 3 PWAs I tried only one works correctly. I tried loading Google Maps but it just hangs and then crashes after a few seconds.
I'm going to keep using Firefox for mobile browsing but I'm reinstalling Chrome for PWAs.
@kyle Another bug about custom tabs and pwa not working unless Firefox is running reduces it's utility.
If you are installing chrome just for pwa consider hermit it lets you customize websites/webapps while having many features like night mode.
@wonderdon Thanks for the suggestion, I'll look into Hermit.
piira.org is one server in the network