I am having same issue. Here is the code that I executed on the portal page.
<script>
function makeChart(rData) {
console.log("Showing all accounts");
console.log(rData);
}
$(document).ready(function() {
$.get('/getAccounts', makeChart, 'json');
});
</script>
And here is what I am having back in the console window. The JQMIGRATE warnings and the makeChart function doesn't run, see the first red box please.

The makeChart function is accessible. See the second red box in the above image please.
And when I execute the jQuery get right from the console window, it returns data in the response text. No JQMIGRATE warnings in the console this time. But the makeChart function still doesn't run. See the third red box.
Please help.