I’ve thought about this myself during a phase of less that then perfect health. I think a somewhat practical solution is to have all passwords and documentation on how to use them/access the services that require them in a (online) password manager (so it stays current). Then have a USB stick with encrypted login credentials and OTP backup deposited at a notary and hand out the decryption key to a few trustworthy friends and family members.
This way nobody can access your stuff and the notary can make sure to hand out the USB stick only to the one person you specified in your will. The other friends family members are there as backup in case your “special” friend has lost the decryption key in the meantime.

I’d love to hear about other solutions though. Maybe there’s a better option.