Firefox

Yes: https://chat.mozilla.org

I would be mad if this would be next to fall since I use it. I don’t self-host Matrix since it is too expensive being built on a fundamental ‘eventual consistency’ model mirroring all text & attachments for all users in every DM & room to your storage—not to mention the Python implementation server & even the Rust one use much more system resources than other open chat options. It’s the same for Mastodon specifically too which but Ruby this time—with eventual consistency chewing up GiBs of storage making small players shut down instances. I would not be surprised tho if their Matrix server fell next just based on hosting cost.

Wanting to get folks off proprietary garbage like Slack, Telegram, & Discord was the right idea but moving to Matrix will prove to be a mistake as nodes are too expensive to run therefore leads to the centralization we need to escape. With the poor performance of the flagship Element client too, casual users think it is too damn slow (literally takes 2 minutes to even get to a screen with text in my browser & it isn’t even done syncing). There are more mature technologies with lower running costs that could have/should have/can be embraced.