Re:Synchronous Messaging at Mozilla: The Decision
by steveklabnik on Thursday December 19, 2019 @11:58AM
(#21836679)
This is sort of correct but also not, exactly. Most of the teams are on Discord, but a few are on Zulip. The Embedded Working Group is on Matrix.
In general, the teams are allowed to organize themselves as they wish.
I suspect they might move back to Mozilla's Riot/Matrix instance once it's set up in production, but that hasn't happened yet.