Yeah I'm now in vacation, so I started looking at the issues. Some are already solved.
The login problem is probably not solved (I didn't modify the phabricator extension), but the phabricator login will need to be replaced by a gitlab login anyway.
The list numbering problem is very strange, I have the same problem with Firefox but not with Chromium.
Is the Special:WhatLinksHere problem still here?
About the language in the search, it should be possible to filter with: https://www.mediawiki.org/wiki/Manual:Hooks/SpecialSearchResults but it will be difficult to get the user language and not having false positive.