Dual authentication methods, LDAP + local Dolibarr database accounts possible?

I’m running Dolibarr 12.0.4 on Ubuntu Server. I have LDAP with Active Directory configured and have imported some accounts from LDAP to Dolibarr. I use ‘userprincipalname’ field as the username field for the LDAP accounts. Some of the users that will be using this Dolibarr installation will not be on this Active Directory server, so they will need local accounts on the Dolibarr system that they can log into. So far I have not had luck combining the two methods so they would both work at the same time.

In conf.php I have the option to have either:
$dolibarr_main_authentication=‘dolibarr’;
or
$dolibarr_main_authentication=‘ldap’;

But how can I have both?