Essentially there should be an endpoint listening to receive CSP error reports. In WordPress you can create a REST API endpoint using the rest_api_init hook to handle CSP reports. Docs are here https://developer.wordpress.org/reference/hooks/rest_api_init/.
The report data that receive via the endpoint can be logged to a file in this case could be the file you created csp-reports
This requires some minimal coding and understanding of the workings of web applications.
Hope this will help you!