MusicBrainz wiki contains interwiki links to many wikis and other web pages. Most of them are classic interwiki links (one can link to them like [[bb:something]] to BookBrainz, see https://wiki.musicbrainz.org/MusicBrainz_Wiki). But two of these are incorrectly configured as language links:

• ab for AcousticBrainz incorrectly classified as a wiki in Abkhazian language
• lb for ListenBrainz incorrectly classified as a wiki in Luxembourgish language

See also https://wiki.musicbrainz.org/Special:Interwiki. This makes several issues:

• One can not link to them like [[ab:something]], you have to use [[:ab:something]]
• Links are handled like pages in Abkhazian/Luxembourgish language by MediaWiki
• API of the wiki for bots and other tools (Pywikibot) returns three wiki language variants instead of one (english, abkhazian and luxembourgish) to the user to choose from

PS: This issue might have been already tracked here, but I can't find any result. See also https://phabricator.wikimedia.org/T130381 and https://phabricator.wikimedia.org/T243669 both reporting wrong wiki interwiki configuration