What you'll need
The Mio app needs to be installed as an app for both external organizations to chat from their preferred platform.
Option 1 - App extension
Go to the universal channel you want the link from. Find the · · · at the bottom of your universal channel and choose Mio.
You'll see a link you can copy and send to your external contacts on Slack or Webex. The URL should start with app.m.io/uc/...
You can also send them a personal email invite by typing their email in the fields below.
Option 2 - Menu
In a direct chat with the Mio app, send "menu". Select My Conversations.
Click the drop down menu and select the universal channel you want to view. Select View.
Copy and paste the link to invite others to the channel. Copy and paste the link to invite others to the channel. The URL should start with app.m.io/uc/...