1. Buy a bunch of Yubikeys, minimum of 2.
2. Create GPG keys and store them on YubiKeys. Follow this guide: https://github.com/drduh/YubiKey-Guide (if you want to, keep the secret keys, but in case of multiple YubiKeys I would not keep them anywhere). Remember to set the keys to always require touch.
3. Use GPG to encrypt your backups to multiple recipients (all of the YubiKeys).
4. Take care of the physical keys with proper storage and procedures. Do not store the keys together, have at least one in a really secure location, check if you have all the keys regularly, etc.
5. Test restores at least once per quarter, with a randomly selected key.
The advantages of this solution is that it is simple, works pretty well, and gets you a lot of mileage with relatively little inconvenience. You don't have the risk of keys being copied, and guarding physical keys is easier than digital ones.
You still have the problem of guarding the passphrases to the Yubikeys (if you use them), but that is much less of a problem than guarding the encryption keys. A passphrase without the physical key is useless.
This setup works for organization from size 1 up to fairly large ones.
Note that some recently fashionable security consultants crap on GPG from great height, but do not provide an alternative. It's a tool that while having multiple flaws, does many jobs better than anything else out there.