Windows NT4 as domain member of 2019 domain

[lexware]

Hi and good afternoon from Graz / Austria,

I am a new member here, already enjoyed reading many of the topics here, which is always good stuff  Nonetheless, there is something that either isn't asked anywhere or one does just get "muzzled" for asking this: In my home lab, I want to try what seems impossible, it absolutely makes no productive sense whatsoever, but I am stuck: I'd like to create a modern-day Windows domain with the most possible different OSes as members.

Having already set up the Windows 2019 DC, DNS, etc. I successfully joined a Win2003 server to it, so far so good. My Windows NT4 is also joined (I got that running by setting various regedit- and GPO-tweaks on the domain controller, which I'd like to repeat is just a home lab server with no productive background  But the NT4 machine is unable to log in to the domain, it always says "The system was unable to log you in, the domain XXXX is not available". Local login works, accessing Netlogon ans sysvol shared work as well (after entering domain\administrator and the proper credentials.

Which tweaks/settings did I possibly miss? I have already set up a WINS-Server in the domain joined 2003 machine, but it didn't resolve the issue. DNS is properly working, all the modern machines are pingable from the NT4 client as well. 

But the machine only sees itself in the network neighbourhood, which is weird and till today, unfixable for me...

I am thankful for every hint 

Sincerely,

Martin