If your gpg key is too valuable for you to feel comfortable with backing it up to the cloud using keysafe, here's an alternative that might appeal more.
Keysafe can now back up some shares of the key to local media, and other shares to the cloud. You can arrange things so that the key can't be restored without access to some of the local media and some of the cloud servers, as well as your password.
For example, I have 3 USB sticks, and there are 3 keysafe servers. So let's make 6 shares total of my gpg secret key and require any 4 of them to restore it.
I plug in all 3 USB sticks and look at
mount to get the paths to them.
Then, run keysafe, to back up the key spread amoung all 6 locations.
keysafe --backup --totalshares 6 --neededshares 4 \ --add-storage-directory /media/sdc1 \ --add-storage-directory /media/sdd1 \ --add-storage-directory /media/sde1
Once it's done, I can remove the USB sticks, and distribute them to secure places.
To restore, I need at least one of the USB sticks. (If some of the servers are down, more USB sticks will be needed.) Again I tell keysafe the paths where USB stick(s) are mounted.
keysafe --restore --totalshares 6 --neededshares 4 \ --add-storage-directory /media/sdb1
Using keysafe this way, physical access to the USB sticks is the first level of defense, and hopefully you'll know if that's breached. The keysafe password is the second level of defense, and cracking that will take a lot of work. Leaving plenty of time to revoke your key, etc, if it comes to that.
I feel this is better than the methods I've been using before to back up my most important gpg keys. With paperkey, physical access to the printout immediately exposes the key. With Shamir Secret Sharing and manual distribution of shares, the only second line of defense is the much easier to crack gpg passphrase. Using OpenPGP smartcards is still a more secure option, but you'd need 3 smartcards to reach the same level of redundancy, and it's easier to get your hands on 3 USB sticks than 3 smartcards.
There's another benefit to using keysafe this way. It means that sometimes, the data stored on the keysafe servers is not sufficient to crack a key. There's no way to tell, so an attacker risks doing a lot of futile work.
If you're not using an OpenPGP smartcard, I encourage you to back up your gpg key with keysafe as described above.
Two of the three necessary keysafe servers are now in operation, and I hope to have a full complement of servers soon.
(This was sponsored by Thomas Hochstein on Patreon.)