Mattermost began as a free & open source self-hostable Slack clone. I deployed it in 2018 on a server and have used it every day since, in support of at-risk environmental defenders. Today it hosts a very large community.

In this time Mattermost has come to be far superior to Slack (which I regretfully have to use weekly), in almost every capacity.

Yet another example where the narrative that truly free software will never eclipse the feature set or productivity of proprietary, is challenged

Matrix/Synapse with Element, while presently not without performance challenges, and a few niggling UI/UX challenges for the less geeky, is coming along nicely as a uniquely end-to-end encrypted team chat solution. It is very close to being the ultimate team chat platform for the At Risk, for mass mobilisation generally. I suspect 2023 will be its year.
@JulianOliver at #GermanZero we‘re using Matrix/Element running in @nico‘s #datacenterlight @ungleich since beginning of 2021 as a Slack replacement.
Meanwhile there is constantly a huge improvement on backend and client. I’ve never regret the decision pro Matrix 👍
@themadhatter @JulianOliver @ungleich At least one who did not regret it! Joke aside, even at ungleich we struggled in the very beginning, but now we have all kind of different user groups, ranging from #anime fans over complex #industrial organisations to schools to #volunteer based organisations. The probably best feature we see is that organisations *do* actually federate and with that build logical organisations. A bit like how the Internet was designed in the first place...