Zulip is also, last I checked, the only ones who offer completely free, archive-enabled, hosted chat for open source projects ( https://zulip.com/for/open-sourc

Zulip is also, last I checked, the only ones who offer completely free, archive-enabled, hosted chat for open source projects ( https://zulip.com/for/open-source/ https://zulip.com/for/open-source/ ). Mattermost has some kind of "out of the kindness of our heart" setup, but it requires applying for it ( https://docs.mattermost.com/about/license-and-subscription.html#do-you-have-a-program-for-official-non-profits-open-source-projects-and-charities https://docs.mattermost.com/about/license-and-subscription.h... ), and Slack appears to actually retain the archive content, but only makes it available for those who pay