For what it’s worth, it is now possible to delete your threads account without also deleting your instagram account.

Not to discredit your arguement but isn’t Signal also centralised?

There’s also GoToSocial which is made to be lightweight from the get go.

You don’t need internet to access the passwords stored in Bitwarden if you have their local clients installed. It stores an encrypted copy of your database locally to your device which syncs (updates) over the internet.