Matrix was built to become the open communication of the web and serve everyone. But, as the Internet and email did, its network effect started with governments. Today, and as proven by the audience in the room, most European governments and several others are either using it or looking at implementing it for their communications. This talk will tell the story of how we got there and why.
I would probably go with one of the ones that supports clustering. if you have that many users, you may very well end up expanding and needing the room to do so. ejabbard has a focus on scalability, and they’ve been around since 2002.
Oh cool Ejabbard support Matrix too! I’ll definitely check it out more!
Honestly covering both kind of covers all the niches I care about (fediverse is another beast on a technical front so I don’t expect overlap persay for those).