Reminder: Alias locales are defined from Unicode Common Locale Data Reposotiory (CLDR) which is loaded by MusicBrainz Server through the package DateTime::Locale.

The latest version 1.37 of this package is built from CLDR 42, whereas the currently used version 1.36 of this package is built from CLDR 41, according to the changelog.

The list of changes is unclear - -"Due to changes in ISO 639, a number of language codes have been deprecated, and some added." - but possibly not affecting much our list of locales. See release notes of CLDR 42 for details.

It must be investigated whether or not any alias in the database must have its locale code updated to work with CLDR 42. The exact list can be added in comment.