[cornel_io]

That has failure modes, though, especially death on one of the N (might seem unlikely but I just had to help a friend unfuck a family member's finances after he died in a car accident next to the one trusted associate who had all his logins saved in an account locked behind 2FA secured by his iPhone which he didn't leave the unlock code to with anyone). I know there are other schemes where you only need M of N to turn the key, but really...

Leave. Your. Passwords. With. An. Attorney. And also your phone unlock code. A reputable attorney (preferably attached to a big firm) won't lose your stuff, and if they die or go out of practice they will have procedures in place to make sure you are set. This is not a situation where you want some clever DIY scheme that might fail and leave your loved ones scrambling to sort your finances when they are already devastated and mourning.

[selcuka]

> I know there are other schemes where you only need M of N to turn the key

That's what OP suggests (Shamir's Secret Sharing).

[highwaylights]

“Oh my, Smith Partners LLC, what big teeth you have”

[avereveard]

Two attorneys. One attorney has failure modes too.

[dividedbyzero]

Better use three attorneys on at least two continents, one of them in the other hemisphere. Otherwise a single medium-size asteroid could easily wipe out all your backups and what then.