The big boys Hash, difference and federate to get round GDPR, I was at a legal conference on the subject a few months ago and a whole new industry of companies selling data federation services has popped up on the back of GDPR. There are 3 primary ways companies can carry on doing what they do without a problem.
hashing - much like they did on PCI (payment cards), they will hash the data (normally multiplying by a modulus) and store the hash, which they can then attribute back to you
difference - they will store a baseline and compare you to the baseline and store the difference.
with hashing and difference methods they store data which cannot be attributed to you, but is easily restorable.
With federation they break up your data and store it in different jurisdictions to avoid a country's specific legislation.