This version assures that admins cannot disable languages using the form at
It is still allowed to use this form to add new languages. Another way to add languages would be using drush and the module Drush Language.
Enabling/disabling languages at the UI for specific domains must be done at
/admin/structure/domain/view/[domain_id]/language. Another way to do this task is using drush, such as:
drush domain-locale-set domain_machine_name 'list of language codes' --default=language_code
drush domain-locale-set usa.example.com 'en es' --default=en
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