The only unified solution with a shared set of platform services and a powerful UI structured around channel-based communications, checklist-based process automation, and card-based task and project management.https://mattermost.com/platform-overview/
My biggest problem with Slack is it’s great for chat, but poor for project management. Yes I can integrate all the apps but the integrations are limited. Mattermost promises Bette project management tools and workflow management. Worth a look.