The secret bits can be protected by a strong passprase (which you can print out) or kept in a hardware device that also does enough of the cryptography to allow

The secret bits can be protected by a strong passprase (which you can print out) or kept in a hardware device that also does enough of the cryptography to allow the secrets to stay on the hardware device. After that the problem becomes one of backup. You can scatter your encrypted keys all over the internet if you want (or just on a reliable server somewhere). You can have a bunch of hardware devices stored in various safe places and protected in various ways. You often hear advice that comes down to keeping, say, your PGP keys in one secure place, but that is a terrible idea... E2EE encryption needs a good backup approach. If your system does not provide that in a easy to use way for the user then you have a bad system. E2EE encryption is hard but it doesn't help to leave all the hardness for the user.