Would GDPR even cover this? I don't see why La Liga would need to include any personal information about the user in their data. They are concerned with identifying the buisness streaming pirated matches, not who is watching.
Edit: The official statement actually answers this
>The codes will not refer to your name, but to your IP address and the specific ID assigned by the PPP when you register.
Edit: The official statement actually answers this
>The codes will not refer to your name, but to your IP address and the specific ID assigned by the PPP when you register.