I think I have also been experiencing this issue. A date passed from a parent feature to child feature in a survey embedded in a dashboard is not being recognised.
Date field in form which should be populated by the date from the url parameter remains greyed out.
To see if any value is coming through via the url the date passed by the url parameter was written to a text field and displays as a formatted date (e.g. Wednesday 1st May 2024, 11:30). When passed to date-time formula in XLS form to try and convert this it returns Invalid format.
Adding other date field instead e.g. CreationDate works albeit drops the time.
It seems like the url parameter is picking up the formatted version of the date string in the parent date field rather than a date value. I tried changing the field formatting using the fields manager in map viewer for the parent layer but no effect.
The workaround was to create a decimal date field for the parent feature which is populated on feature creation. This is then passed from parent to child via the url parameter and converted back to date using the date-time function and used to populate the date field in the child feature.