It has helped, and that is something I'm grateful for.
The same goes for me.
By "Edit Field Group" error warning from jQuery Migrate Helper: /wp-content/plugins/meta-box-aio/vendor/meta-box/meta-box-builder/assets/js/angular.min.js: jQuery.fn.attr('selected') might use property instead of attribute
/wp-content/plugins/meta-box-aio/vendor/meta-box/meta-box-builder/assets/js/angular.min.js: jQuery.fn.attr('selected') might use property instead of attribute
I found the cause: WP Update 5.5.3 -> jQuery update to 3.5.1 -> without jQuery Migrate the backend works incorrectly.