CmdExec on MS-SQL 2019 Linux

I’m trying to add a CmdExec as task in a job, on MS-SQL 2019 on Centos8. However, the task always fails with "running the requested program is not allowed". I have tried specifying both /bin/true and true as the program, but these also fail.

Is there a list of authorised programs for CmdExec, and is this is editable? I found that MS-SQL Linux 2017 doesn’t support CmdExec, but I think this has been fixed in 2019