Me and a lot of colleagues have done documentation collaboratively with https://hackmd.io/ which also comes as an open source fork as https://hedgedoc.org/. The first has commenting function, the latter hasn't. Both make it easy to do doc sprints synchronously which means everybody is on the phone at the same time and write down documentation. As you do this with Markdown you can use your writing with https://squidfunk.github.io/mkdocs-material/ e.g. which is a static site generator running on Python and build beautiful documentation from Markdown files. If you want to build with https://gohugo.io/ I recommend https://www.docsy.dev/ theme.

We do scholarly writing and documentation with GitLab which we host on-premise. GitHub and GitLab come with sophisticated workflows for commenting and quality assurance if you learn to branch and merge which is for a lot of folks a steep learning curve. To onboard colleagues I recommend starting with HedgeDoc first and then migrate to more advanced workflows with Git(Lab|Hub).