In the early 2000s, attempting to deploy a Jabber server at my first employer, I needed a user manual for the Windows (95!) jabber client I wanted the users to use (not that any of them actually read the manual!)
I co-operated with the lead developer at the time to produce an “official” manual in Docbook XML V4. The original XML is sadly lost (not that I’d ever want to do that again!), but the PDF-rendered version is available here.