Man all this self-custody how to guides I've found to teach illiterates on Reddit and you're over here on stacker news...ugh nevermind, here: https://glacierprotocol.org/docs/overview/multi-signature-security/

Additionally, Bitcoin is information. You can have a multi-signature set up (with the people who handle your will if you like) wherein the people who will inherit your Bitcoin will learn your seed phrase and other instructions.