Mio does not sync people profiles in universal channels since the app is posting messages using impersonation.
However, you can view a list of all members in each channel by following the instructions below.
How do I view all members in my universal channel?
How to view all members in Microsoft Teams.
How to view all members in Slack.
How to view all members in Webex.
To add your own feature requests, let us know about your use case by commenting on our roadmap board.