Yup this is the way. The resulting .kdbx database file is encrypted so you can even synchronize it over an untrusted provider. Otherwise you can use something like syncthing to keep it strictly peer to peer.

That is basically what they do yes. ISPs are the only thing standing in between the entirety of humanity and out of the box selfhosting. With fixed IPv6 IP addresses you could build and sell devices that just self host all your stuff out of the box. You could just sell complete normie people a “cloud box” that they can slap in their home for a one time cost that will take care of all their cloud storage and smart device needs. You could integrate it into smartphone OS ootb so that all you have to do is scan a QR code on the “cloud box” and it connects all your apps that need it to it.