Ask HN: Open-Source Chat Platform Matrix, Rocketchat, Mattermost, ...

I am looking for an Open Source Chat Platform for around 1k non-tech users. I thought it is easier on the market... Matrix: For non-tech end users still quite complicated when dealing with keys, encryption, etc Rocketchat: Moved a lot of features to the enterprise version and the community edition is not really sufficient for such a use case Mattermost: Moved some features to enterprise as well and the clients (especially Android) still encounter performance problems (e.g. startuptime of several seconds) Do you know any good alternatives?