@GuMean - the workaround used to involve turning Classic controls back on, and then changing the Format of the classic Date picker control. Unfortunately this feature has now been retired.
You could update the Default property of the DataCard (not the Data Card Value) with:
Text(ThisItem.'Your Date Field', "[$-en]mm/dd/yyyy hh:mm")
However, this is pointless because the field will default back to the incorrect format each time you re-select the record or make an update.
If you have a "View" mode for your form, an alternative option is to hide the Date picker control when the Form is in View mode and instead display a Label with the correct formatting for the saved Date.
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