item.php override contains the following code:

<script type="text/javascript">
window.addEvent('domready', function(){
SqueezeBox.assign($$('a.k2Modal'), {
parse: 'rel'
});
});
</script>

When a page containing the code is opened in a browser the following error is generated:

Uncaught TypeError: window.addEvent is not a function

Perhaps it is a matter of using an obsolete MooTools function (I just upgraded to K2 2.9.0 and Joomla 3.9.5), but I have no idea what to use instead of this. Can you direct me the right way?

Can you please advice where I can 'add data-k2-modal="image" to the <a> element wrapping your main K2 item image' - so it is applied to every article (K2 item)?