This is going to test verification so we don't forget about the required follow up task :)

Notes from the task inspection (some possible directions to start this off):

• find the origin of https://doc.wikimedia.org/Wikibase/master/php/md_docs_topics_entitytypes.html and use the markdown as comparison source (haystack)
• make sure all the public consts of the EntityTypeDefinitions class are present in the markdown

Note from task inspection for possible inputs to check:

This is waiting for the next OOUI release, may be verified after that.

I'm moving this to stalled instead of closing it since the probability of this issue not being solved is high

Task inspection note: we could start by checking what code adds the ui-entityselector-input-unrecognized class to the input.

@Lydia_Pintscher task inspection question:
Having looked into this our assumption is that the checkbox to suppress redirects should in fact not play a role and only the fact of a namespace being supported or not influences whether the sitelink gets updated or deleted. Can you confirm this?