The JS trigger I am asking about is acf/setup_fields. This is triggered when ACF fields are added to a wordpress post/page. And re-triggered every time new fields are added such as in a repeater.
The post you linked to is talking about issues with a different action (the php action acf/register_fields which used to be used in v4 when adding new field types).
Unless I am missing something, the pages you linked to are not related to my question (although I do appreciate your effort to help). Please correct me if I am wrong and I am missing something.
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