Alternatives to Slack

From Kanthaus wiki

In the past we used Slack for internal coordination. We looked for alternatives and after an ukuvota we decided to migrate to Mattermost.

sign up app UI
email phone number Use nextcloud

account (SSO)

web mobile desktop distinct levels
Slack yes no ? yes yes yes 3 (workspace), channels, messages, replies
Mattermost yes no paid yes yes yes 3 (instance), channels, messages, replies
Zulip yes no yes yes yes yes 3 (instance), channels, topics, messages
Signal no required no yes required yes 1 (group), messages
Simplex no no no yes required no 1 (group), messages
Discourse yes no yes yes yes no 2.5 [forum] (instance), categories, topics, replies

2.5 [chat] (instance), channels, messages, replies

Mailing lists yes no no yes yes yes ? (list), messages & replies
Matrix yes no ? yes yes yes 4 (instance), space, group, message, thread

External comparison resources