The current advice for redirects in GitLab pages is to use meta refresh tags, which is a fairly poor experience for people used to building 1000-line-long nginx configuration files full of redirects.
Is there scope for adding a simple redirect configuration specifically for GitLab pages? It could then serve the redirects itself as a HTTP 30x response. It'd just need a simple format text format specifying sourceurl, desturl, and optionally HTTP code (301/302/etc).
SSGs like Hugo could then write extension modules to take their lists of aliases and generate this file, rather than HTML pages for each.