The four registry mods are:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\LanmanWorkstation\Parameters]
“DomainCompatibilityMode”=dword:00000001
“DNSNameResolutionRequired”=dword:00000000
The above need to be added to allow the join to work. Then find the key below and set those values to 0.
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\Netlogon\Parameters]
“RequireSignOnSeal”=dword:00000000
“RequireStrongKey”=dword:00000000
This is definitely reported to work on many occasions across the 'net but doesn't for me. I may be being jinxed by having done an in-place upgrade and although I have a spare machine to try an install with, I haven't yet found the time.
Note that it is reported that you still get an error about the DNS suffix after these mods but the connection works - there is some Samba chatter about DNS suffixes but I only half understood it and since I haven't got that far yet, I didn't apply myself to it