Hi, LLI , I can guide you through sorting this out, if you like.
The PWA runs in any browser, but you have to make concessions that ( just like everyone else in the world 😩) they do not properly test with any other browser engine than chromium, so functionality is ... slow ... to stay properly good.
Ostensibly, though, if you install the PWA Add-on / Extension (soon to be subsumed into the mainline code - or a version / mozilla version therein) then you can make PWAs for literally anything, really. I have mine running 3 different tenancies, currently, via the Multi-Account Containers. ;)
Find me on my LinkedIn vanity of eliot dot cole if you need more. 👍
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Relatedly, though ... It would be nice for BASE application functionality to be enabled in the PWA, though ... because if we are able to (for example) add a background image to our meetings (and for it to stick) then we should be able to do it in the Web App without premium add-ons.