Since october ‘19: mendixcommunity.slack.com
You do not need an invite for https://mendixcommunity.slack.com/
Just create a slack account and join this workspace.
I don’t have no “@mendix.com” and no “@jhu.edu” email address. how can i join the Mendix Slack channel?
I don’t think there is one, you could raise this on the idea forum.
How can I get an invite to the Mendix Slack channel?