Actually none of the buttons in the edit view is working (exception made for the help button).
This is also true for the other edit views of the component:

administrator/components/com_users/views/group/tmpl/edit.php
administrator/components/com_users/views/level/tmpl/edit.php
administrator/components/com_users/views/note/tmpl/edit.php
administrator/components/com_users/views/user/tmpl/edit.php

The problem is that the form id has been changed.
The buttons call the Joomla.submitbutton() function and the Joomla.submitbutton() calls the Joomla.submitform() function.

	/**
	 * Default function. Usually would be overriden by the component
	 */
	Joomla.submitbutton = function( pressbutton ) {
		Joomla.submitform( pressbutton );
	};

The Joomla.submitform() function is looking for the form id "adminForm".

	/**
	 * Generic submit form
	 */
	Joomla.submitform = function(task, form, validate) {

		if (!form) {
			form = document.getElementById('adminForm');
		}

If this is not intentional and is not part of a planned development process, we need to revert the form id to "adminForm".

Yes that's it. I've tried placing the form-validate class in the form html and it worked.

Changed a few days ago with this PR #14710.

Check #14931

Ah ok right ;) I was going to make a PR to fix that.

@rjcf18 please make a PR for all the rest forms that are missing the form-validate class

Thanks @dgt41

Sure will do that @dgt41 .