Is there any platform that can be secured and compliant with relevant privacy laws and regulations, such as the General Data Protection Regulation (GDPR) or the California Consumer Privacy Act (CCPA)?
Depends what you are considering a "platform". Almost any Unix variant can do it if you are willing to do the mods and keep up the maintenance for both the base and your adds.
Another non-traditional approach would be the use of Block-Chain tech, but it would not qualify under the standards you mentioned. Could be an elegant solution to the problem though.