As far as I know the best option is still printing a newly created address and private key on archive quality paper and putting it in a bank safe deposit box. I

As far as I know the best option is still printing a newly created address and private key on archive quality paper and putting it in a bank safe deposit box. If you don't ever spend from that address the key should be safe. Best practice is to use an airgapped computer running a live CD so the key will never have been on a network. It should be easy to find tutorials on paper wallets. It's not user friendly for sure, but if you want to protect a large amount of Bitcoin it's the best option.