Dynamically populate a field’s choices based on another field

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I'm looking to do more or less exactly what's described in this ACF guilde - update a field's choice values based on the value of another field: https://www.advancedcustomfields.com/resources/dynamically-populate-a-select-fields-choices/

In my case I have an options field that I which to access to set the choices for a block field.

Any help is much appreciated!

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I've elected to use the WP Customizer to add this setting as I'm then able to access it inside ACF Builder. Going to leave this open incase anyone has another idea. Would love to hear it.