[Samba] is "map untrusted to domain" possible?

[d tbsky]

hi:

   at RHEL 7.4 we had used "map untrusted to domain = yes". so users
can login with "username" instead of "sam-dom\username".

   after upgrade to RHEL 7.5, samba version upgrade from 4.6 to 4.7.
now "map untrusted to domain = yes" or "map untrusted to domain =
auto" are not working.

   can we still let user to use "usename" instead of
"sam-dom\username" like old days?

   thanks a lot for help!!