A fix is something like this:

diff --git a/ipaserver/plugins/idviews.py b/ipaserver/plugins/idviews.py
index a68b03915..7d0bff3c8 100644
--- a/ipaserver/plugins/idviews.py
+++ b/ipaserver/plugins/idviews.py
@@ -715,8 +715,12 @@ class baseidoverride(LDAPObject):
                 self.backend,
                 self.override_object,
                 keys[-1],
-                fallback_to_ldap=options['fallback_to_ldap']
+                fallback_to_ldap=options.get('fallback_to_ldap', False)
             )
+            if (len(keys[:-1]) == 0 and
+                    self.override_object is 'user' and
+                    anchor.startswith(SID_ANCHOR_PREFIX)):
+                keys = (DEFAULT_TRUST_VIEW_NAME, ) + keys

         keys = keys[:-1] + (anchor, )
         return super(baseidoverride, self).get_dn(*keys, **options)

FreeIPA 4.6.3 has been released, moving to FreeIPA 4.6.4 milestone

master:

• 676774d kdb: handle enterprise principal lookup in AS_REQ
• 28389fe Add design page for managing IPA resources as a user from a trusted Active Directory forest
• ecc0a96 support using trust-related operations in the server console
• 973e0c0 idviews: handle unqualified ID override lookups from Web UI
• bee4204 Support adding user ID overrides as group and role members
• 306304b tests: account for ID overrides as members of groups and roles
• 0ba64b1 Web UI: allow users from trusted Active Directory forest manage IPA
• 9248d23 ipatests: test that adding Active Directory user to a role makes it an administrator

ipa-4-8:

• 6abade3 kdb: handle enterprise principal lookup in AS_REQ
• afe9191 support using trust-related operations in the server console
• 2ffb4fd idviews: handle unqualified ID override lookups from Web UI
• 8cce2bb Support adding user ID overrides as group and role members
• 5e8df37 tests: account for ID overrides as members of groups and roles
• 99e613e Web UI: allow users from trusted Active Directory forest manage IPA
• 6b0f8f3 ipatests: test that adding Active Directory user to a role makes it an administrator