TYPO3 File Reference Fields Required using a small Require JS Modul (Title, Alternative, Description...)

ext_localconf.php

<?php
if (!defined('TYPO3_MODE')) {
	die('Access denied.');
}

\TYPO3\CMS\Extbase\Utility\ExtensionUtility::configurePlugin(
	'TGM.' . 'tgm_copyright',
	'Main',
	[
		'Copyright' => 'list,sitemap',

    ],
	// non-cacheable actions
	[
		'Copyright' => 'sitemap',
    ]
);

if (TYPO3_MODE === "BE" && true === version_compare(TYPO3_branch, '9.5', '>=') ) {
    if(true === (bool) \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Core\Configuration\ExtensionConfiguration::class)
        ->get('tgm_copyright', 'copyrightRequired')) {
        $pageRenderer = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Core\Page\PageRenderer::class);
        $pageRenderer->loadRequireJsModule('TYPO3/CMS/TgmCopyright/RequiredFileReferenceFields');
    }
}

RequiredFileReferenceFields.js

define(['jquery'], function($) {

    $(document).on('t3-formengine-postfieldvalidation',function() {
        validateReferenceFields();
    });

    $(document).on('change','.t3js-form-field-eval-null-placeholder-checkbox input', function() {
        validateReferenceFields();
    });

    function validateReferenceFields() {
        var $referenceFields = $('.t3js-formengine-placeholder-formfield input[type="hidden"][name$="[copyright]"]');
        $referenceFields.each(function() {
            var $parentFieldGroup = $(this).closest('.t3js-formengine-palette-field');
            if($(this).parents('.t3js-inline-record-deleted').length === 0) {
                if(false === $parentFieldGroup.find('.t3js-form-field-eval-null-placeholder-checkbox input').is(':checked')
                    && $parentFieldGroup.find('.t3js-formengine-placeholder-placeholder input').val().toString() === '') {
                    $parentFieldGroup.addClass('has-error');
                } else if(true === $parentFieldGroup.find('.t3js-form-field-eval-null-placeholder-checkbox input').is(':checked')
                    && $(this).val().toString() === '') {
                    $parentFieldGroup.addClass('has-error');
                } else {
                    $parentFieldGroup.removeClass('has-error');
                }
            } else {
                $parentFieldGroup.removeClass('has-error');
            }
        });
    }


});

Line 12 of the JS is made to fit only with the related extensions "copyright"-field of File References. But this selector can be replaced to fit any other field of file references like the title or alternative text.