Es hat ein wenig gedauert bis ich mal wieder Zeit gefunden habe mich ein wenig mit UCS zu beschäftigen.
Die erste Hürde war rauszufinden, wieso das alte Forum nicht mehr "funktioniert" - hat ein paar Minuten gedauert bis ich den Hinweis auf den Umzug gefunden habe 
Leider war der Umzug meines Forum-Users genauso problembehaftet wie die ganze UCS AD Takeover/Synchronisationsgeschichte bisher. Login mit dem alten User/Passwort wurde verweigert - glücklicherweise hat wenigstens der Passwort-Reset funktioniert - aber im Ernst, ein 10stelliges Passwort für ein Forum??? Ist nicht etwas Overkill? 
getestet - keine Fehler gefunden.
Habe ich ebenfalls ausprobiert => keine Änderungen des Verhaltens.
Inzwischen habe ich die AD Takeover Geschichte aufgegeben und den Versuch ad Acta gelegt - dann wird es wohl doch ein Windows Domain Controller bleiben...
18.03.17 12:43:35.667 DEBUG_INIT
18.03.17 12:43:35.809 LDAP ( PROCESS ) : Renaming 'cn=Domain Admins,cn=groups,dc=testdomain,dc=local' to 'Domänen-Admins' in UCS LDAP.
18.03.17 12:43:35.810 LDAP ( WARN ) : rename cn=Domänen-Admins
18.03.17 12:43:35.830 LDAP ( PROCESS ) : Renaming 'cn=Domain Users,cn=groups,dc=testdomain,dc=local' to 'Domänen-Benutzer' in UCS LDAP.
18.03.17 12:43:35.830 LDAP ( WARN ) : rename cn=Domänen-Benutzer
18.03.17 12:43:35.851 ADMIN ( WARN ) : No settings/cn superordinate was given.
18.03.17 12:43:35.852 LDAP ( PROCESS ) : Modifying 'cn=default,cn=univention,dc=testdomain,dc=local' in UCS LDAP.
18.03.17 12:43:35.852 ADMIN ( WARN ) : No settings/cn superordinate was given.
18.03.17 12:43:35.859 LDAP ( PROCESS ) : Renaming 'cn=Domain Guests,cn=groups,dc=testdomain,dc=local' to 'Domänen-Gäste' in UCS LDAP.
18.03.17 12:43:35.859 LDAP ( WARN ) : rename cn=Domänen-Gäste
18.03.17 12:44:40.821 DEBUG_INIT
18.03.2017 12:44:41,856 MAIN (------ ): DEBUG_INIT
18.03.2017 12:44:41,896 LDAP (ERROR ): Failed to lookup AD LDAP base, using UCR value.
18.03.2017 12:44:41,949 LDAP (PROCESS): Building internal group membership cache
18.03.2017 12:44:42,116 LDAP (PROCESS): Internal group membership cache was created
18.03.2017 12:44:42,127 LDAP (PROCESS): Using testdomain as AD Netbios domain name
18.03.2017 12:44:42,230 LDAP (PROCESS): Scan all changes from UCS ...
18.03.2017 12:44:42,939 LDAP (PROCESS): initialize AD: last USN is 0, sync all
18.03.2017 12:44:43,353 LDAP (PROCESS): sync to ucs: [ container] [ modify] CN=Users,dc=testdomain,dc=local
18.03.2017 12:44:43,381 LDAP (PROCESS): sync to ucs: [ container] [ modify] CN=Computers,dc=testdomain,dc=local
18.03.2017 12:44:43,435 LDAP (PROCESS): sync to ucs: [ user] [ add] uid=Gast,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:43,796 LDAP (PROCESS): sync to ucs: [ group] [ add] cn=Domänencomputer,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:44,243 LDAP (PROCESS): sync to ucs: [ group] [ add] cn=Zertifikatherausgeber,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:44,346 LDAP (PROCESS): sync to ucs: [ group] [ add] cn=RAS- und IAS-Server,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:44,444 LDAP (PROCESS): sync to ucs: [ group] [ add] cn=Richtlinien-Ersteller-Besitzer,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:44,546 LDAP (PROCESS): sync to ucs: [ group] [ add] cn=Domänencontroller,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:44,630 LDAP (WARNING): group_members_sync_to_ucs: failed to identify object type of ad member, ignore membership: CN=IGM48,OU=Domain Controllers,DC=testdomain,DC=local
18.03.2017 12:44:44,637 LDAP (PROCESS): sync to ucs: [ group] [ add] cn=Organisations-Admins,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:44,750 LDAP (PROCESS): sync to ucs: [ group] [ modify] cn=Domänen-Gäste,cn=groups,dc=testdomain,dc=local
18.03.2017 12:44:44,761 LDAP (ERROR ): failed in post_con_modify_functions
18.03.2017 12:44:44,762 LDAP (ERROR ): Traceback (most recent call last):
File "/usr/lib/pymodules/python2.7/univention/connector/__init__.py", line 1309, in sync_to_ucs
f(self, property_type, object)
File "/usr/lib/pymodules/python2.7/univention/connector/ad/__init__.py", line 157, in set_univentionObjectFlag_to_synced
connector.lo.lo.lo.modify_s(univention.connector.ad.compatible_modstring(ucs_object['dn']), [(ldap.MOD_REPLACE, 'univentionObjectFlag', flags)])
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 364, in modify_s
return self.result(msgid,all=1,timeout=self.timeout)
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 465, in result
resp_type, resp_data, resp_msgid = self.result2(msgid,all,timeout)
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 469, in result2
resp_type, resp_data, resp_msgid, resp_ctrls = self.result3(msgid,all,timeout)
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 476, in result3
resp_ctrl_classes=resp_ctrl_classes
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 483, in result4
ldap_result = self.ldapcall(self.l.result4,msgid,all,timeout,addctrls,add_intermediates,add_extop)
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 106, in ldapcall
result = func(*args,**kwargs)
NO_SUCH_OBJECT: {'matched': 'cn=groups,dc=testdomain,dc=local', 'desc': 'No such object'}
18.03.2017 12:44:44,762 LDAP (WARNING): sync to ucs was not successfull, save rejected
18.03.2017 12:44:44,762 LDAP (WARNING): object was: CN=Domänen-Gäste,CN=Users,DC=testdomain,DC=local
18.03.2017 12:44:44,768 LDAP (PROCESS): sync to ucs: [ group] [ modify] cn=Domänen-Benutzer,cn=groups,dc=testdomain,dc=local
18.03.2017 12:44:44,785 LDAP (ERROR ): failed in post_con_modify_functions
18.03.2017 12:44:44,785 LDAP (ERROR ): Traceback (most recent call last):
File "/usr/lib/pymodules/python2.7/univention/connector/__init__.py", line 1309, in sync_to_ucs
f(self, property_type, object)
File "/usr/lib/pymodules/python2.7/univention/connector/ad/__init__.py", line 157, in set_univentionObjectFlag_to_synced
connector.lo.lo.lo.modify_s(univention.connector.ad.compatible_modstring(ucs_object['dn']), [(ldap.MOD_REPLACE, 'univentionObjectFlag', flags)])
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 364, in modify_s
return self.result(msgid,all=1,timeout=self.timeout)
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 465, in result
resp_type, resp_data, resp_msgid = self.result2(msgid,all,timeout)
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 469, in result2
resp_type, resp_data, resp_msgid, resp_ctrls = self.result3(msgid,all,timeout)
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 476, in result3
resp_ctrl_classes=resp_ctrl_classes
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 483, in result4
ldap_result = self.ldapcall(self.l.result4,msgid,all,timeout,addctrls,add_intermediates,add_extop)
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 106, in ldapcall
result = func(*args,**kwargs)
NO_SUCH_OBJECT: {'matched': 'cn=groups,dc=testdomain,dc=local', 'desc': 'No such object'}
18.03.2017 12:44:44,785 LDAP (WARNING): sync to ucs was not successfull, save rejected
18.03.2017 12:44:44,785 LDAP (WARNING): object was: CN=Domänen-Benutzer,CN=Users,DC=testdomain,DC=local
18.03.2017 12:44:44,789 LDAP (PROCESS): sync to ucs: [ group] [ modify] cn=Domänen-Admins,cn=groups,dc=testdomain,dc=local
18.03.2017 12:44:44,808 LDAP (ERROR ): failed in post_con_modify_functions
18.03.2017 12:44:44,808 LDAP (ERROR ): Traceback (most recent call last):
File "/usr/lib/pymodules/python2.7/univention/connector/__init__.py", line 1309, in sync_to_ucs
f(self, property_type, object)
File "/usr/lib/pymodules/python2.7/univention/connector/ad/__init__.py", line 157, in set_univentionObjectFlag_to_synced
connector.lo.lo.lo.modify_s(univention.connector.ad.compatible_modstring(ucs_object['dn']), [(ldap.MOD_REPLACE, 'univentionObjectFlag', flags)])
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 364, in modify_s
return self.result(msgid,all=1,timeout=self.timeout)
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 465, in result
resp_type, resp_data, resp_msgid = self.result2(msgid,all,timeout)
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 469, in result2
resp_type, resp_data, resp_msgid, resp_ctrls = self.result3(msgid,all,timeout)
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 476, in result3
resp_ctrl_classes=resp_ctrl_classes
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 483, in result4
ldap_result = self.ldapcall(self.l.result4,msgid,all,timeout,addctrls,add_intermediates,add_extop)
File "/usr/lib/python2.7/dist-packages/ldap/ldapobject.py", line 106, in ldapcall
result = func(*args,**kwargs)
NO_SUCH_OBJECT: {'matched': 'cn=groups,dc=testdomain,dc=local', 'desc': 'No such object'}
18.03.2017 12:44:44,808 LDAP (WARNING): sync to ucs was not successfull, save rejected
18.03.2017 12:44:44,808 LDAP (WARNING): object was: CN=Domänen-Admins,CN=Users,DC=testdomain,DC=local
18.03.2017 12:44:44,815 LDAP (PROCESS): sync to ucs: [ user] [ modify] uid=Administrator,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:44,912 LDAP (PROCESS): sync to ucs: [ group] [ add] cn=Schema-Admins,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:45,70 LDAP (PROCESS): sync to ucs: [ group] [ add] cn=WINS-Benutzer,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:45,169 LDAP (PROCESS): sync to ucs: [ group] [ add] cn=DHCP-Benutzer,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:45,273 LDAP (PROCESS): sync to ucs: [ group] [ add] cn=DHCP-Administratoren,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:45,386 LDAP (PROCESS): sync to ucs: [ group] [ add] cn=DnsAdmins,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:45,487 LDAP (PROCESS): sync to ucs: [ group] [ add] cn=DnsUpdateProxy,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:45,587 LDAP (PROCESS): sync to ucs: [ group] [ add] cn=Sysadmins,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:45,682 LDAP (PROCESS): sync to ucs: [ group] [ add] cn=IIS_WPG,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:45,772 LDAP (PROCESS): sync to ucs: [ ou] [ add] OU=Rechner,dc=testdomain,dc=local
18.03.2017 12:44:45,798 LDAP (PROCESS): sync to ucs: [ group] [ add] cn=CVSUser,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:45,888 LDAP (PROCESS): sync to ucs: [ group] [ add] cn=CVSAdmin,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:45,994 LDAP (PROCESS): sync to ucs: [ group] [ add] cn=Domänen-Sicherungsoperatoren,cn=users,dc=testdomain,dc=local
18.03.2017 12:44:46,95 LDAP (PROCESS): sync to ucs: [ user] [ add] uid=testadmin,ou=benutzer normal,ou=benutzer,dc=testdomain,dc=local
18.03.2017 12:44:46,302 LDAP (ERROR ): Unknown Exception during sync_to_ucs
18.03.2017 12:44:46,303 LDAP (ERROR ): Traceback (most recent call last):
File "/usr/lib/pymodules/python2.7/univention/connector/__init__.py", line 1281, in sync_to_ucs
result = self.add_in_ucs(property_type, object, module, position)
File "/usr/lib/pymodules/python2.7/univention/connector/__init__.py", line 1135, in add_in_ucs
return ucs_object.create() and self._modifycustom_attributes(property_type, object, ucs_object, module, position)
File "/usr/lib/pymodules/python2.7/univention/admin/handlers/__init__.py", line 305, in create
return self._create()
File "/usr/lib/pymodules/python2.7/univention/admin/handlers/__init__.py", line 759, in _create
self.lo.add(self.dn, al)
File "/usr/lib/pymodules/python2.7/univention/admin/uldap.py", line 382, in add
raise univention.admin.uexceptions.ldapError(err2str(msg), originalexception=msg)
ldapError: No such object
18.03.2017 12:44:46,303 LDAP (WARNING): sync to ucs was not successfull, save rejected
18.03.2017 12:44:46,303 LDAP (WARNING): object was: CN=Thomas Wagner (Admin),OU=Benutzer normal,OU=Benutzer,DC=testdomain,DC=local