This week I installed samba on a raspberry pi running Ubuntu server to provide active directory domain services to my home network. The Windows computers in the house are now joined to the domain. It was easy and quick to setup. There are a ton of guides to setting up samba as an AD domain controller on Ubuntu out there.

Best I found: https://www.univention.com/products/ucs/functions/

UCS core is free and runs windows compatible active directory. Not sure they have a pi4 version though.

Removing the network connection might still work? Windows 10 could be installed and activated fully offline (activated via "slui 0x4" command that gives you 9 six digit numbers and tells you to call a number based on your location; after you enter them, you get 8 six digit numbers back to activate).

From another comment it sounds like you might not actually need to join a domain, it will just let you make a local account so that you can join a domain later.

https://news.ycombinator.com/item?id=30390857

A fake local KMS server has been the way most activation hacks have worked for years actually

If you want to get creative you can run your own KMS server and anyone who connects to your local network can now be assigned whatever microsoft license you want. You don't even need to fake it or use the hacked version - just run a real one and get a bunch of edu licenses for whatever products you want to activate for whoever connects to your local network.

Samba can work as an Active Directory DC, but I have never gotten around trying it: https://wiki.samba.org/index.php/Setting_up_Samba_as_an_Acti...

Samba can easily be configured as a DC.