I do not have a working example. This example does not work with the new ACF JS API https://github.com/Hube2/acf-dynamic-ajax-select-example/tree/master/dynamic-fields-on-relationship but it does something similar. It loads other fields based on a relationship field.
This one has a working example of doing an AJAX request based on a select field change https://github.com/Hube2/acf-dynamic-ajax-select-example/tree/master/dynamic-select-example.
When working with repeaters you must target the row where the updated field was changed.
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