With fresh install seems to work...
This is an extract of the console error from the updated site:
jQuery.Deferred exception: _ is not defined transform/options.ajax.processResults/items<@https://mydomain.com/wp-content/plugins/meta-box/js/select-advanced.js?ver=5.6.7:44:7
transform/options.ajax.processResults@https://mydomain.com/wp-content/plugins/meta-box/js/select-advanced.js?ver=5.6.7:41:37
e</n.prototype.query/e/e<@https://mydomain.com/wp-content/plugins/meta-box/js/select2/select2.min.js?ver=4.0.10:2:37844
e@https://mydomain.com/wp-admin/load-scripts.php?c=0&load%5Bchunk_0%5D=jquery-core,jquery-migrate,utils&ver=6.0.2:2:30038
Deferred/then/l/</t<@https://mydomain.com/wp-admin/load-scripts.php?c=0&load%5Bchunk_0%5D=jquery-core,jquery-migrate,utils&ver=6.0.2:2:30340
undefined