MySQL - Truncated incorrect datetime value
In would recommend
  SELECT CONVERT( '2020-06-01T09:38:08+02:00' , DATETIME)

STR_TO_DATE does the trick, but is usually slow.
You can run such a Query to test the performance using the column name instead of the text
 CREATE TABLE t2 (tz TIMESTAMP) SELECT CONVERT( '2020-06-01T09:38:08+02:00' , DATETIME)