In the documentation https://developer.mozilla.org/en-US/docs/Web/Progressive_web_apps/Guides/Installing mozilla says you need to install this extension.
https://addons.mozilla.org/en-US/firefox/addon/pwas-for-firefox/
However it says the extension is not actively monitored. Is this feature supported by firefox or not? It seems tacked on and unsupported.
What’s confusing here is that MDN content is not solely written by Mozilla - see e.g. @[email protected]. So it’s probably not Mozilla saying you need to install this extension.