mattermost-desktop: mattermost-desktop (open-source Slack alternative) mattermost-desktop: mattermost-desktop: This is the desktop client app for Mattermost, an open-source Slack mattermost-desktop: alternative. mattermost-desktop: mattermost-desktop: Homepage: https://mattermost.com mattermost-desktop: mattermost-desktop: mattermost-desktop: mattermost-desktop: mattermost-desktop: