Like T95822, but for:
P̶l̶e̶a̶s̶e̶ ̶u̶p̶d̶a̶t̶e̶ ̶t̶h̶i̶s̶ ̶d̶e̶s̶c̶r̶i̶p̶t̶i̶o̶n̶ ̶i̶f̶ ̶y̶o̶u̶ ̶f̶i̶n̶d̶ ̶a̶n̶y̶ ̶m̶o̶r̶e̶.̶
Steps for migrating at https://phabricator.wikimedia.org/T95822#1469641 (simple case) and https://phabricator.wikimedia.org/T91715#1160062 (advanced case).
I attempted to apply @Krinkle's edits on metawiki (but they didn't seem to fix the issue, at least on the page that I tested) and enwikibooks (but my template edit is stuck in FlaggedRevs review)
Per https://phabricator.wikimedia.org/T91715#1160062 there was one critical step missing: Removing the default output case that creates a (sysop-only visible) red link.
This is the main reason for the whole construct. This must be removed from the core Editnotice template and (optionally) added back via MediaWiki:Editnotice-notext. That way, when there is no editnotice declared for a page, the template truly results in no output when parsed. - Which is used as indicator by MediaWiki core to determine whether or not there is an editnotice.
So the part that I missed out was the Template:Editnotice_load/core edit: https://meta.wikimedia.org/w/index.php?title=Template:Editnotice_load/core&diff=prev&oldid=15467858
Need to figure out what to do about enwikibooks & FlaggedRevs, then complete the job there.
I wrote a script to find more like that, the result is T134949: Fix "1 notice" on more wikis