This is really fascinating. I’m on this journey, too, and do a lot that’s similar, but I’ve not heard of some of what you do/use and some of it sounds beyond my capabilities.

Thirded. I self-host it (actually the Vaultwarden fork) and use it on desktop browsers, as a desktop app, and as and Android app (F-Droid). I also store secure notes in it (e.g. end of life instructions for my partner). Very powerful and versatile, and AFAICT, secure.

That sounds crazy, but easy to test. Thanks for the suggestion.

I use Solokeys. Didn’t know they were defunct. I just bought another from then a month or so ago. I use it for MFA, ssh, and sudo, and I’m trying to config Kubuntu login screen to require solokey but no luck yet.

I like solokeys, but the one I recently bought has NFC and, technically, my pixel7 running GraphenreOS can detect the device, but it doesn’t work. Many people reported this issue. In my experience, NFC is non-functional.