Users are able to successfully configure a `ldap-realm` via a custom configuration, however it is not possible for them to update the authentication mechanisms of the default endpoint due to ISPN-14327. It's necessary for users to configure a non-digest auth mechanism in order for direct-verification to work:

https://access.redhat.com/documentation/en-us/red_hat_data_grid/8.3/html-single/data_grid_security_guide/index#ldap-security-realms_security-realms