[Samba] Error joining Samba 4.7.4 DC to existing Win2008R2 domain

[Claudio Nicora]

> No, I was just checking if you where something you shouldn't, like
> creating the zone files in the Bind configs.
Good, it's better to clear out any doubt.

> There doesn't seem to be anything wrong in any of your conf files, the
> only other thing I can think of is, is Avahi running on the new DC ?
> and this only applies if your TLD is '.local'

No, it's not:
===
root at srvad-new:~# apt remove avahi*
Reading package lists... Done
Building dependency tree
Reading state information... Done
Note, selecting 'avahi-ui-utils' for glob 'avahi*'
Note, selecting 'avahi-daemon' for glob 'avahi*'
Note, selecting 'avahi-dnsconfd' for glob 'avahi*'
Note, selecting 'avahi-autoipd' for glob 'avahi*'
Note, selecting 'avahi-utils' for glob 'avahi*'
Note, selecting 'avahi-discover' for glob 'avahi*'
Package 'avahi-autoipd' is not installed, so not removed
Package 'avahi-daemon' is not installed, so not removed
Package 'avahi-utils' is not installed, so not removed
Package 'avahi-discover' is not installed, so not removed
Package 'avahi-dnsconfd' is not installed, so not removed
Package 'avahi-ui-utils' is not installed, so not removed
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
===

And no, my domain is not .local but each log I post was automatically 
cleaned up in a case-sensitive way ;)
MYDOMAIN --> SAMDOM
mydomain --> samdom
.EXT --> .LOCAL
...

Another thing that comes to my mind is that the 2008R2 domain was 
upgraded from an initial Win2000.
Win2000-->Samba direct migration is not possible because Samba requires 
at least a Win2003 domain.
So the complete upgrade was Win2000 (SRVAD-OLDOLD) --> Win2008R2 
(SRVAD-OLD) --> Domain/forest functional level upgrade --> Samba 4.7.4 
migration.

Could there be something wrong/unexpected in current Win2008R2 domain 
config?
It seems not to me because Windows client machines work ok and the 
domain seems to function properly.

Claudio

>
> I know that 4.7.5 will join to a Samba AD DC, but this is with Debian.

That's good