Yes, both Slack and Desku offer a Free Trial.
Slack is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Desku is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Pricing for Slack Starts at $2.67/Month whereas for Desku Starts at $19/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 Desku includes Zoho Desk, Zendesk Support, ManageEngine ServiceDesk Plus, Freshservice, MessageDesk, Freshdesk, LiveAgent, HelpDesk, SysAid, Jitbit Helpdesk, eStreamDesk, UseDesk, HelpdeskEddy, Desk360, BoldDesk and Alerty.