Yes, both Pivotal Tracker and Slack offer a Free Trial.
Pivotal Tracker is designed for Large Enterprises, Medium Business and Small Business.
Slack is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Pricing for Pivotal Tracker Starts at $6.50/User/Month whereas for Slack Starts at $2.67/Month.
Some top alternatives to Pivotal Tracker includes monday.com, Quickbase , Smartsheet, ClickUp, Zoho Projects, Jira, Wrike, TeamGantt, Teamwork, ProjectManager.com, Microsoft Project, Backlog, Trackboard, Quick Base, Projectsly by 500apps, Height and Project Insight.
Some top alternatives to Slack includes Microsoft Teams, Glip, Google Chat, ChatWork, Dialog, Office Chat, imBee, Takle, SPACE Channel and Teamwork Chat.