New Teams advertising PopUp Message

Hi All,
over 4000 users use ms teams in our company. the use of the MS Teams app via cell phone is not supported and we have communicated this to our users.
Since the new MS Teams, however, exactly this message appears with the Mobile Teams app login (see pic).
Where can I change the settings so that this message does not appear?

I have admin access to the MS Teams Admin Center but I don't see a setting to deactivate such messages.

Thanks for short feedback and help

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