I know you're joking, but safety deposit boxes aren't nearly as safe as you think they are. (https://www.nytimes.com/2019/07/19/business/safe-deposit-box...)

Not totally joking after some thought. If the problem that a person experienced is "complete loss of bank account" then having a physical backup - not at a bank! - would help to cater to that scenario.

And yeah, looks like that's not a foolproof solution either. 3rd backup option might be needed... :D