We could reproduce the issue. Turns out this is related to a recent change with the for update clause. This is not working correct on MariaDB.

For now you can work around it by turning the Use_Select_For_Update off in This file is located in DataFlex 20.0\bin64 and in DataFlex 20.0\bin
It should look as follows:
; Use_Select_For_Update 0
;       Determines if a Select with For Update clause is used for Finds inside transactions.
;       Select For Update will lock the record inside transaction.
;    Normally the ODBC driver specifies if Select For Update can be used (SQL_CA1_SELECT_FOR_UPDATE),
;   but the MySQL/MariaDB ODBC driver does not return this correct.
;   For MySQL/MariaDB set to 1
Use_Select_For_Update 0
This should make the error go away.

We are working on a definite fix for the issue.