To reproduce:
- Go to https://af.wikipedia.org/wiki/Nederland
- Click the "more languages" in the end of the languages list.
- Search for Nedersaksies.
Observed: Nedersaksies (nds-nl) doesn't appear.
Expected: It must appear under Europe and also when searching for "neder".
One thing I noticed is that the lang attribute of the language link for this language is "nds-NL" rather than "nds-nl" as I'd expect. Maybe browsers or HTMLtidy, or something else at some stage normalizes language code prefixes that are country names to upper case, but this is just a guess. If I go to getInterlanguageList() and change this.getAttribute( 'lang' ) to this.getAttribute( 'lang' ).toLowerCase(), it fixes this issue, but there may be a better solution.
High priority, because all bugs about missing languages are triaged as such.
First reported at https://www.mediawiki.org/wiki/Topic:T7cyivsztzge738k .