There is an issue with Moroccan Amazigh (zgh) test Wikipedia in Wikimedia Incubator. It cannot been set as language of interface. And we cannot translate pages to this language. For example, try to translate the Main page in Wikimedia Incubator, it will give you a broken interface. I've noticed that it is considered as undefined language. I don't know what's the problem. Thanks.
Hi, thanks for reporting. This is expected, see https://translatewiki.net/wiki/Portal:Zgh and https://meta.wikimedia.org/wiki/Language_proposal_policy#Requisites_for_final_approval
Please complete https://translatewiki.net/w/i.php?title=Special:Translate&group=core-0-mostused&language=zgh (currently 8 % translated) and then the language will be added to MediaWiki.
P.s.: I also wrote at https://translatewiki.net/wiki/Thread:User_talk:Amara-Amazi%C9%A3/Thanks_for_your_translations as the user was translating non-MediaWiki messages.