add_filter( 'mastodon_api_instance_translation_languages', function( $translation_languages ) {
    $translation_languages['en'] = array( 'de', 'es', 'fr', 'it', 'ja', 'nl', 'pl', 'pt', 'ru', 'zh' );

    return $translation_languages;
} );

apply_filters( 'mastodon_api_instance_translation_languages', array() )