Yes, both Slack and Airbrake offer a Free Trial.
Slack is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Airbrake is designed for Large Enterprises, Medium Business and Small Business.
Pricing for Slack Starts at $2.67/Month whereas for Airbrake Starts at $29/Month.
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 Airbrake includes Sentry, Bugsnag, Zoho BugTracker, Rollbar, TrackJS, BugHost, Bug-Track.com, Disbug, EventSentry and Crash Catch.