Internet calling services and firefox 52.9

[Sergiaws]

Disclaimer. This isn't exactly an XP question, but I think that XP users could know more about this and help me. I'm considering to get a KaiOS device/dumbphone, and these devices most of the time use a pre-quantum firefox engine which is the same as Firefox 52.9 and Roytam browsers for XP. Whatsapp calls are not available there, so I want to know if there is some kind of kalling service available for Firefox 52.9/similar browser and a device with 512mb of ram. What options could I consider?

[NotHereToPlayGames]

I think, though not positive, that the only reason Google Voice does not work in 52.9/similar is that the permission dialog for microphone access does not seem to work.

Unsure why, older versiosn of Firefox and Forks had a microphone access setting directly in the permissions page, newer versions no longer have this global mic access via global permissions.