I'm surprised you lot didn't go with Matrix and Riot. I believe they have decent IRC integration, and some clients (like WeeChat, my client of choice - though I appreciate it's a bit hardcore) have direct support for the Matrix protocol.
I only have direct experience with one. Inkscape's solution is really good. Apart from having by far the
best support I've ever received from a free software community, hands down, they have a wonderful HTML5<->IRC bridge.
Your can find the HTML version on
https://chat.inkscape.org/. I asked in their channel, turns out it's based on rocket.chat. I don't know how trivial it is to set up, it looks like a complex piece of kit but let me say it works fantastically for their art-focused community, where they constantly share image and vector files with each other.
You just wasted 3 seconds of your life reading this.