While it serves us well in many cases, our current approach that each Item can have only a sitelink to one single page per wiki has some substantial drawbacks:

• wikis that support articles in multiple scripts only can only have a sitelink for one script (see T278366 and User:Nikki/Permanent_duplicates#Multiple_linguistic_representations)
• incubator cannot be properly supported with sitelinks because contains multiple "wikis"
• commons has pages for the same concept in different namespaces (see T206426, User:Nikki/Permanent_duplicates#Multiple_namespaces)
• pages existing in multiple languages via the Translate extension don't have sitelinks for their translated versions (see T348507)
  • conversely, linking to a T154181#5243963
• some wikis have multiple projects (wikitionary, wikivoyage, ...) in different namespaces: (User:Nikki/Permanent_duplicates#Multiple_projects)
• something about aliases of species (T303667)

See the subtasks for details.

(This task intentionally does not yet suggest an approach to tackle this, but aims to bring together tasks describing symptoms of a similar underlying problem from different perspectives.)