When you add the Power BI report as a tab in Microsoft Teams the date format is shown as US format mm/dd/yyyy.
The date format is fine in Power BI desktop and on the Power BI (browser) as long as you set the right language in your browser.
However the Android mobile app and Teams desktop app still show the wrong format.
I have searched the forums but have only found a bug in the past that they say is now fixed.
The date format is in a slicer and a card to show when it was last refreshed.
I have set the region on the user setting in microsoft teams.