So on Wikipedia:Special:PrefixIndex using the parameter "|hideredirects=yes" will not show redirects, but when trying it on Fandom it doesn't seem to work (the same goes for "stripprefix="). How can get this to work?
It looks correct to me. I believe the issue is that Wikia's fork of MediaWiki was done prior to the introduction of those parameters. In other words, the version Wikia is using doesn't have that capability. I remember trying a long time ago and it wasn't working then either. It should work once the UCP is done; whenever that is.
Can you not hide it with css? You can change cursivity, color and apend a message with .allpagesredirect, surely there's a way to hide it/turn it so grey/make it blend in with the bg that it's sorta hidden