Yes, both Slack and Redbooth offer a Free Trial.
Slack is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Redbooth is designed for Large Enterprises, Medium Business and Small Business.
Pricing for Slack Starts at $2.67/Month whereas for Redbooth Starts at $9/user/month when yearly.
Some top alternatives to Slack includes Microsoft Teams, Glip, Google Chat, ChatWork, Dialog, Office Chat, imBee, Takle, SPACE Channel and Teamwork Chat.
Some top alternatives to Redbooth includes Quickbase , Smartsheet, ClickUp, Zoho Projects, Wrike, TeamGantt, Asana, Teamwork, ProjectManager.com, Microsoft Project, ProWorkflow, nTask, Taskworld, Trackboard, Quick Base and Height.