For DataFlex 19.1 you should not set the Character Set to utf8mb4, but leave empty or set to latin1.

The Character Set setting defines in what format the MySQL ODBC driver returns data to the DataFlex ODBC driver:
-The DataFlex 19.1 ODBC driver expects data as ansi, so character set should be an ansi encoding like latin1.
-The DataFlex 20.0 OBDC driver expects data as utf8, so character set should be set to utf8mb4.