Ah thanks 🙂
I ended up doing trial and error, and found this as a solution:
// where field_609b103fcd576 is a sub-field in my repeater
acf.addAction("new_field/key=field_609b103fcd576", function ($field) {
$field.on("change", function (e) {
var value = $field.val();
console.log(value);
});
});
Not sure if it’s the optimal one, but it worked 🤷♀️