We’ll its a private key, so just a few kb of data. You can likely put it on all sorts of devices. Most services that use it will require some of the above, so I doubt the usefulness, but the same goes for most passwords.

Im curious how you access your passwords with the above criteria. Are you using a notepad with dozens/hundreds of unique passwords, some kind of dice based randomizer, or just a few passwords for many sites?

Nope. The private key can be backed up, stored in an online password vault, copied automatically to other devices, whatever.

There are good and simple answers to this issue.

Passkeys are becoming the industry standard. They are better in nearly every way, but would not have been possible before smartphones.

They are unique for each site, not breachable without also having a users device, not phishable, and can’t be weak by design.

Rancher is owned by Suse, which is mainly a solid steward in the community.

They also have k8 frontend called Harvestor. It can run VMs directly, which is nice.

An Anne frank fold out phone would be a hell of an art piece. I think it could give Lisa Frank a run for her money.