@dangoodin when I started working at Mozilla all group communication was on IRC. It wasn't until 2014 that Slack became a thing inside the org, and initially it was mostly used by people outside of the tech sphere (management, marketing, etc...). Several teams moved there over time, but I didn't like it as I was used to our communication channels that weren't company-only, but also open to contributors and the general public. My teams stayed on IRC first, then moved to Matrix.