Save or export your private and public Slack messages, threads, files, and users locally without admin privileges.
Mattermost is an open source platform for secure collaboration across the entire software development lifecycle..
bridge between mattermost, IRC, gitter, xmpp, slack, discord, telegram, rocketchat, twitch, ssh-chat, zulip, whatsapp, keybase, matrix, microsoft teams, nextcloud, mumble, vk and more with REST API (mattermost not required!)