Best solution for this issue may still be paper. It is undetectable by professional equipment and you can laminate and hide it just anywhere, as opposed to hardware wallets which may already have who-knows-what kind of flaws and backdoors inside them. Since they have been specifically created with cryptocurrency cold storage as a purpose, expect anything and everything from them. I am talking particularly about Ledger, as it has closed-source components inside.
Hide a seed on a piece of paper in two different locations and choose two other separate spots to hide the seed's very long, random passphrase at. Should they ever get to own your piece of paper, they will find out it contains a balance of exactly zero Bitcoins inside.
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Regards,
PrivacyG