MySQL date and datetime formats unrecognised by Data Studio

I had the same issue. My approach to solve this is to modify the date format within Google Data Studio by creating a new dimension, reformatting the mySQL Datetime into the desired format.

In your example you use DATE_FORMAT. I wonder if you apply this in Data Studio (which does not know DATE_FORMAT) or in mySQL?. If you do it in data studio and leave your mySQL/phpmyadmin untouched you can use this:

TODATE(your-date-field, 'DEFAULT_DASH', '%Y%m%d')

This will take the date format YYYY-MM-DD with optional time in HH:ii:ss and reformat it into YYYYMMDD which works with data studio.