I've never been able to run PWA on Firefox for linux, only using Chromium. I don't even thing they work on windows. And from a quick internet search it appears

I've never been able to run PWA on Firefox for linux, only using Chromium. I don't even thing they work on windows. And from a quick internet search it appears there is no official support, although apparently you can install a third party extension+app on linux to support it