Yes, both Slack and Clappia offer a Free Trial.
Slack is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Clappia is designed for Large Enterprises, Medium Business and Small Business.
Pricing for Slack Starts at $2.67/Month whereas for Clappia Starts at $5/User/Month when Billed 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 Clappia includes Quick Base, AppElixir, Nwicode, NoCodeZ, Zoho Creator, Appy Pie, Zeroqode, 2OS App Builder, DrapCode, Codeless and Zappter.