jQuery datepicker localization not working in 3.5.1/1.12.1

Just upgraded to v8.1.2 from 7.22.
Was trying to update my process to use latest jQuery version (3.5.1 and ui.1.12.1), but it broke date pickers localization.
My JS code is :

<script type="text/javascript" src="/wfgen/js/common/jquery.ui.datepicker-localize.js"></script>
	if (typeof $selectedObject === "undefined") {
		function pageLoad() {
				dateFormat: "dd/mm/yy"

It works fine with 1.10.2 and ui.1.10.3 versions, but console.log outputs “undefined” when switching to new version.
Then, I added code from datepicker-fr.js instead of the included one (/wfgen/js/common/jquery.ui.datepicker-localize.js), and this one makes it work too.
Any help would be highly appreciated :pray: