How Does Advanced Data Protection Affect 2Do for Web?
If you use Advanced Data Protection (ADP), try signing in with your Apple Account email address, password and verification code instead of a passkey. Enter these details only on Apple's sign-in page, and use your normal account password, not an app-specific password.
2Do's ordinary task fields and smaller notes use standard iCloud encryption. ADP protects the CloudKit assets used for attachments and large notes stored in iCloud. Web uploads pass through our transfer service, which receives the content before forwarding it to Apple. Those transfers use encrypted connections; they are not end-to-end encrypted between your browser and Apple. See Apple's iCloud data security overview.
Bear, another CloudKit app, documents this sign-in method with ADP enabled. We have not verified full 2Do for Web compatibility with ADP.