I have written several 500 page documents in libreoffice both as sole author and as one of two or three primary contributors. It works quite well because it is

I have written several 500 page documents in libreoffice both as sole author and as one of two or three primary contributors. It works quite well because it is easy to define styles and virtually never apply direct formatting. There would no doubt need to be a plugin to force this behavior in a large group. Multiple Indices and Tables of Contents were also well supported. More advanced tooling can still be used since it is an xml based file format (like MS office at this point I believe). For example I could write a complex regex to create different rules for applying an index without too much fuss. On most or all of those docs I was collaborating with others (editors etc) using track changes. It worked fine for us. But that was always under a dozen people in the group. There are various simple odt to git solutions available. Now I am not necessarily advocating this path, but we were philosophically opinionated on this point in our groups, so we were happy to do it. Latex is not excellent for authoring, although I understand it can be a necessary evil for documents with a lot of formulas or other difficult to format constructs. There is a lot to be said for the simplicity of a WYSIWYG editor when writing, so you can focus cleanly on the content you are trying to write.