[Feedback]: Needs info on joining a Samba AD-DC to and existing domain

### Page URL

https://documentation.ubuntu.com/server/how-to/samba/provision-samba-ad-controller/

### Select an option

- [ ] I found what I was looking for
- [ ] I couldn't find what I was looking for
- [ ] I found the information, but it was incorrect
- [x] I found the information, but it was incomplete
- [ ] I found the information, but it was confusing
- [ ] I encountered a technical issue (e.g., broken link, image not loading)

### Issue Description

I did find this, but some info was slightly off for Ubuntu.
https://wiki.samba.org/index.php/Joining_a_Samba_DC_to_an_Existing_Active_Directory

Also I would like an article for setting it up to use BIND DLZ instead of Samba internal

Start with the provision-samba-ad-controller page and compare it with the linked Samba wiki article. Identify which joining steps are inaccurate or missing for Ubuntu, and clarify the requested BIND DLZ coverage. Done means the documentation addresses the reported omissions with an Ubuntu-specific, actionable procedure.

Written by the indexing model from the issue text.