Well, I always dreamt about encrypting my master keys to all my digital heritage with some threshold scheme encryption like Shamir's secret sharing. I believe there is some Linux tool available: http://point-at-infinity.org/ssss/

That way N out of M of my friends would have to gather after my passing, combine the puzzle pieces and be granted with access to my stuff.

There are easier ways, though. You can just write down a password and include it with your last will, seal it and have a notary take care of it. I'd create a seperate administrator account/password for that.

You could set up two factor authentification and give them one factor now, and have the other factor stored with your things so they can collect it after your passing. Doesn't need to be complicated, create a password with 30 characters, split it in the middle and you have two factors.

There are online services for these kind of things. Or you can run some dead man switch yourself. I'm not sure what kinds of projects someone would use for that. Taking care of a dead man switch would be annoying for me.

Vaultwarden let's you designate someone to take over your account if they request it and you don't respond within a week

Of you already have a will the most secure, proof idiot way I'd to add that key + instructions to the will. Get some lawyers on board for that and it will work.

If you still have concerns about having the full key on a single place, add a topt or second way of identification and distribute it between your heirs.

Sometime, the old fahion way is the best one by far.

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 an 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.

The alternative to an online pw manager would be a local one that you synchronize to your friends and only the notary has the key to unlock the database, which they only hand out according to your will.

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

P.S.: There are tools to have more redundancy on USB sticks and so on, so that bit flips/degradation can be accommodated. Multiple redundant data carriers are an option as well.

Vaultwarden's readme says that it supports the Bitwarden Emergency Access feature. Why not use that?