Yes, both Slack and Guru offer a Free Trial.
Slack is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Guru is designed for Large Enterprises, Medium Business and Small Business.
Pricing for Slack Starts at $2.67/Month whereas for Guru Starts at $14/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 Guru includes GitBook, Zoho Wiki, KBPublisher, Drupal Wiki, LearnLode Enterprise, TWiki, Wiki Valley, GoGoWorx, HuForce and ProProfs Knowledge Base.