Great question! End-to-end encryption (E2EE) adds an extra layer of security to protect user data. I recommend using the Web Cryptography API for encryption/decryption in the browser, and generating keys using Libsodium for further security.
In my experience, implementing E2EE can be quite challenging. AWS KMS or Google Cloud KMS can simplify key management and provide a higher level of security.
Keep in mind that you should implement proper user authentication for E2EE. Using JSON Web Tokens (JWT) can ensure that only authorized users access the encrypted data.