If you are following best practices, you would be using a device with a password (ideally full disk encryption, but whatever) to access the password manager in the first place. Using just biometrics to log into PC or phone is a bad idea. Most phones require a password/passcode for first unlock due to disk encryption.
Yeah, porting the kernel is the “easy” part for any OS. Its the user space and building up a software ecosystem for the new architecture that is a pain in the ass.