tml_ms_render_blog_signup_language_field()

function tml_ms_render_blog_signup_language_field() {
    $markup = '';

    // Site Language.
    $languages = tml_ms_signup_get_available_languages();
    if ( ! empty( $languages ) ) {

        $lang = get_site_option( 'WPLANG' );

        // phpcs:disable WordPress.Security.NonceVerification.Missing -- read-only: pre-fills the field's default selection, not processed/acted on.
        if ( isset( $_POST['site_language'] ) ) {
            $lang = $_POST['site_language'];
        }
        // phpcs:enable WordPress.Security.NonceVerification.Missing

        // Use US English if the default isn't available.
        if ( ! in_array( $lang, $languages, true ) ) {
            $lang = '';
        }

        $markup .= wp_dropdown_languages(
            array(
                'echo'                        => false,
                'name'                        => 'site_language',
                'id'                          => 'site-language',
                'selected'                    => $lang,
                'languages'                   => $languages,
                'show_available_translations' => false,
            )
        );
    }

    return $markup;
}

View src/includes/ms-functions.php, line 1123 on GitHub