MediaWiki
Thanks to WikiPedia, almost everyone today knows what a wiki is. A MediaWiki is ideal for working as a team on texts.
In anticipation of customer projects, I installed a MediaWiki in such a way that I can quickly set up a separate area with its own access authorizations for new customer projects so that we can then work together on the specification.
A wiki is of course also well suited for other types of documentation. I have set up an area for myself for the documentation of installation and customizing. This wiki is released for everyone to read.
Admittedly, this documentation is kept very brief, just as detailed as I need it for my purposes. But maybe it will still help one or the other with their own installation.