Problems to join Debian/Ubuntu machines to a domain

Ran into this exact Message stream modified error on Ubuntu 24.04 and Windows Server 2025. I tried the Samba workaround (--client-software=samba), but it failed with realm: No such realm found due to Ubuntu's default DNS stub resolver.

Here is how to fix it using the clean, native SSSD method instead:

The Cause

Windows Server 2025 blocks legacy, predictable computer passwords by default. When Ubuntu's adcli tries its standard handshake, the DC abruptly drops the connection.

The Fix

1. Delete the Broken AD Object: Open Active Directory Users and Computers on your DC and delete the orphaned Ubuntu computer object from the failed attempt, or the next join will fail.
2. Disable the GPO Setting: On your DC, open Group Policy Management (gpmc.msc) and edit the Default Domain Controllers Policy.
3. Navigate to: Computer Configuration ➔ Policies ➔ Windows Settings ➔ Security Settings ➔ Local Policies ➔ Security Options.
4. Set Domain controller: Refuse setting default machine account password to Disabled.
5. Run gpupdate /force in a command prompt on the DC.

Now, just run your original native join command on Ubuntu.