The best protection is "don't own anything worthwhile stealing". Failing that -
Spread your risk. Hardware devices are cheap. Don't just own one. Own multiples. Different types of storage in different locations.
100 wallets are safer than everything in 1 wallet.
Keep your seed in a separate location from your hardware device.
Plan for
all eventualities.
Have a pre-arranged plan for what to do if a robbery occurs.
Armed robbery is relatively low risk compared to other methods of theft or loss due to an external event.
Consider destruction due to fire, earthquake, war, volcanic eruption, hurricane, flooding, tsunami, solar flare, EMP, death, paralysis, theft by someone close to you, hackers, seizure by authorities, exchange collapse.
Have a backup plan if you lose physical access to a hardware device. (e.g. the secure deposit box is no longer accessible.)
Hardware devices can also be "hacked" if the hacker has physical access to it. So if you have it in a location you cannot control it can be accessed by thieves or the authorities.
Avoid linking your private details to your online identity.