Great to know that the issue has already been resolved and thanks for sharing the solution so that others experiencing the same thing can easily reference this! Since the Microsoft Q&A community has a policy that the question author cannot accept their own answer. They can only accept answers by others, I'll repost your solution in case you'd like to Accept the answer.
Case Title: MSGraph Remove-MgTeam
Issue Symptom: trying to execute the Remove-MgTeam in Powershell, but I'm getting a 405 error.
Resolution: Please use module MicrosoftTeams as suggested here works
Thanks for your understanding and support.
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