I feel like matrix is an overkill for something like this personally, because I wan't to be motly only used for quick help with peple around the globe and matrix is more generally used to communicate with a huge amount of people around the globe.
Main reason also why I didn't go with matrix is because in my eyes it's still inmature and requires a good amount of maintenance, for what I think of as a simply a quick and dirty server to quickly help people in a more real time setting.
I don't mind people not liking the fact that it's a mattermost server and not wanting to sing up only for this community, it's their choice after all.