The wiki at https://wiki.sogo.nu/StartingPage is outdated. The first three links under "Official Documentation and Help" are going nowhere (404). Then the links under "External Links" are all older than 10 years. And all gray links are pointing to non existent pages.

From my point of view the wiki can be removed totally. (Don't forget to remove the link on the community support page.)

If you want to keep this information then I would recommend to copy those few pages over to github and create there some wiki pages in the sogo project. Then people can at least edit them again and make merge requests.