Recently while designing the custom page, we realized that the format property is missing for the Date Picker control. This is because Date Picker control is based on Fluent UI Library.
One option earlier was to enable the Classic Controls from Settings
And replace the existing control with the classic control
Also, check – https://debajmecrm.com/get-todays-date-format-dates-in-power-apps-canvas-app/
Hope it helps..