Slack link leads to unknown channel (perhaps private channel?)

[absoludity]

Impacted sections

All pages - the slack icon/link is in the header .

Issue Description

The slack icon in the website header links to: https://app.slack.com/client/T1P59QFMF/C05R8DD2AKZ which, I'm not certain, but may be a private channel, or require an invitation? I'm sure it works fine if you're already a member, but all that I see when clicking (I'm authenticated in slack) is:

Perhaps the link should be an invitation link rather than a link to a channel?