Hi there @tycrek! ✌🏻Maker of Cryptee here!
First off – big fan of degoogle, thank you for all the good stuff!
I'm not sure if it works offline when run as a PWA.
Yes it does. In fact on the landing page we talk about this :
And for desktops, you can install it using any desktop browser that supports PWA installations. So Brave, Edge etc all support installing it as well. However there are numerous bugs with their implementations, so we don't recommend it on the landing page to make our helpdesk's life easier.
On the desktop, the only exception is Firefox. And as for why not Firefox, seems like team FF didn't want to add this to desktop in the interest of "not duplicating the efforts by Microsoft / Windows" (comment 15 / last line) https://bugzilla.mozilla.org/show_bug.cgi?id=1407202#c15😅
But from the looks of that thread, things are moving forward, and they're about to add it to desktop as well.
On mobile pretty much all browsers allow PWA installations, Firefox, Opera, even Samsung Internet 😅