As insane as it sounds, cloud backup may be the best option there.
Discussion
Totally agree
And perhaps even just actively choosing somewhere to live that isn't prone to natural disasters specifically as a seed protection strategy I think is a reasonable, depending on stack size
But how do you store the password to decrypt the cloud backup?
First in your brain, maybe with anothet highly trusted human, then backed up in a bank vault in a completely different location, like other side of country, in the rare chance you die/lose memory
Let's put all my keys to my self-sovereign/ p2p/ incensurable/ freedom/ decentralized/ be your own bank/ don't trust verify money in a centralize bank vault.
Don't do that, read the answer about keeping a decryption key there
On its own any banker doesn't know what it opens or the location of the encrypted material
Or split secrets like ZenGo wallet? Or Ledger recover?