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If you're interested in joining one, there are Discord communities with thousands of active users discussing those very things. One of the more generic ones being MechKeys [1], but once you find some designers you like or more niche communities there are dedicated servers most likely for those as well.

[1] https://discord.gg/mechkeys

There is also Geekhack (geekhack.org) and Keebtalk (www.keebtalk.com).

I have built a number of keyboards, and have found all the information I have needed on Geekhack.

Why not just go to /r/mechanicalkeyboards? There's a big community there already, and if they don't already have a Slack or IRC channel you could create it with them.