One additional issue I found with trying to use relativeURLs=true and a baseurl of “/” (which you have to do or you can’t use .RelPermaLink, etc., as explained above)…
404 pages are fairly unworkable, at least for gitlab pages. You would want to use a correct baseurl setting for them, since you can’t know what the path will be that they’ll be served from, then use absURL or relURL, .RelPermaLink, .PermaLink, etc. for the links inside. As is, I can’t see a reliable way to even provide a link back to the home page.