Secrets in IT, part one:
Basic things are hard for even seasoned IT professionals, not to mention average non-it people.
Basic things like authentication. Basic things like backups. Basic things like the combination of those two.
Let's start from the authentication end of things: you're using a password manager right?
Ok. Is it dependent on a single company / closed source components? Pretty much anyone not using KeePass(x(c)) fail this. Companies get compromised, get shut down or acquired.
You've got your open-source password manager syncing seamlessly between your devices. How do you handle 2FA logins?
Do you use your password manager to provide TOTP? Congrats, you no longer have a _second_ factor.
Do you use an independent second factor like a security key or authenticator app? Great, until...you want to combine auth and backups. You always have backups right?
You never store your backup login methods in your password manager right? Because then it's no longer second factor and no longer a backup then.
You have a backup process/tool right? You never store backup account logins in your password manager right? (When you want to restore a bricked device or after a home fire, if your password manager data is not there and the offsite backup credentials are in the pw manager data, chicken and egg problem much?)
Final point: this is hard even if carefully map out how to make it work. There isn't a solution nowhere close enough that would work with little or no thought from users and require minimal maintenance over the years, that would gracefully deal with hundreds of user accounts accumulated over the years, that would gracefully deal with device rotation, 2FA rotation over the years.
@szbalint not really a solution to all the problems that you mention but I think it covers a bunch of them: I use pass with the companion android app (and openkeychain). Sync by storing everything in a git repo. Takes a bit of work to setup but is quite simple to maintain. No solution for 2FA though.
memoryandthought.me is one server in the network