Views has some internal "language codes" that can be used in language filters (and elsewhere in views configurations), in place of fixed language codes like 'en' and 'es', to represent:
a) The detected/selected/negotiated Content language
b) The site default language
These have been updated:
a) Content language: Used to be '***CURRENT_LANGUAGE***'; now '***LANGUAGE_language_content***'
b) Site default language: Used to be '***DEFAULT_LANGUAGE***'; now '***LANGUAGE_site_default***'
Views configurations with these codes in them will need to be edited to use the new codes.
In addition, the detected/selected/negotiated UI language has a code that was not present before: '***LANGUAGE_language_interface***'.