Hello Nick V,
Thank you for reaching out to the Microsoft Community. My name is Eunice and I'm happy to help.
I am sorry you are experiencing this problem. It is possible to create new channels in the Teams Admin Center as a public channel. When you add a new team, you have the option to set the team as either private or public. Here's a quick guide on how to do it:
- Go to the Teams Admin Center.
- Navigate to Teams > Manage teams.
- Click Add to create a new team.
- In the Add a new team pane, you can give the team a name and description.
- Set the privacy to public to make it a public team.
This will allow you to create a team that is accessible to everyone in your organization, and not just by invitation, as is the case with private teams. Remember, you can also manage the privacy settings of existing teams by selecting the team and then choosing Edit.
Reference: https://learn.microsoft.com/microsoftteams/manage-teams-in-modern-portal
Let me know if you need more help.
Regards, Eunice