External Guests being invited to channel meetings

ongrieh , stevecousins I have been chasing this problem as well. What I have figured out is that behind the scenes of the Team is a MS365 group and all Guest Users are automatically designated as 'Subscribers' of the group, regardless of team setting on "AlwaysSubscribeMembersToCalendarEvents" and "AutoSubscribeNewMembers". I presume this is because they can't directly interact with the Team/Group and self-subscribe or join channel meetings ad-hoc. However, this is not ideal because guests then get invited to _every_ channel meeting without explicitly inviting them.

The only way I can find to remove guests as subscribers is via PowerShell. You can view group/team Subscribers with Get-UnifiedGroupLinks -Identity [team name] -LinkType Subscribers. You should see the Guest accounts listed as 'MailUser' recipient types with #EXT# on the name. You can remove these with Remove-UnifiedGroupLinks -Identity [team name] -LinkType Subscribers -Links [Name]. Allow a few moments for the subscriber list to update.

This does not remove guests from their Member role, but now they won't be email-invited to every channel meeting. I haven't confirmed it yet, but it is possible that Guest Accounts get re-subscribed from some unknown trigger. That plus additional guests getting auto-subscribed necessitates creating a script to routinely unsubscribe guests.

Microsoft should fix Teams to honor "AlwaysSubscribeMembersToCalendarEvents" and  "AutoSubscribeNewMembers" on Guest accounts.