Tying to a physical location actual serves an important function in that it introduces an asymmetry between you and a potential attacker / identity thief - it's much cheaper for you to physically show up at your local courthouse to contest something than it is for an attacker to fly in. Any suggestions for how to solve this?
I dunno, that kind of starts with the assumption that people live at one address, in one country. This is what I'm pointing out: that assumption is not true.
I accept that I'm an edge case, but a large minority of (for example) Australians have dual nationality, and will have lived in either of the countries that they're citizens of for long periods of time. Some haven't settled on one yet, and skip back and forth every few months/years. All of them (us) have stories of identity systems, bureaucracy and banks not understanding that they moved country.
You're asking for a replacement asymmetry when the thing you're replacing in the first place isn't actually useful.
But, to answer the question: email is the one thing I'm pretty sure that I and I alone can get to. I have two email addresses, from different providers, using 2FA (google Authenticator on my phone). The 2FA bit is probably enough asymmetry.
However, even that, I could lose: if I fall into a swimming pool while carrying my backpack and phone, I'd have a hard time proving who I am to anyone until I got everything back up and running. Even worse, if I fell into a swimming pool while moving accommodation I'd have my passports in my backpack... not a comforting thought at all.
