Following yours, the best option is write it down on paper. 
But for most sites, for example cryptocurrency exchanges, you can recover your 2FA by using ID or passport.
But for most sites, for example cryptocurrency exchanges, you can recover your 2FA by using ID or passport.
But that paper can be lost or ca be burned (extreme circumstances). Is it not safe to store them on mail or some cloud with proper encryption of course? I personally write them on notepad, encrypt it and then email it to myself.
I have a better suggestion. Download some app like evernote, save all your passwords and keys there. Now create an email ID and don't use it for any other purposes. Sign in in evernote using that email ID and encrypt the app. There. Now you can access your keys anywhere, on any device with no chances of losing them. Also safe and secure.
Encrypted or not, once you start storing your 2FA code in the cloud to be able to access it from anywhere you are kinda killing the purpose of 2FA. Or to be more precise -- once the same device that you use to enter your password can also be used to access your 2FA key, you lose the "2 Factor" part of 2FA. Just a heads up.
How many times you had to access your 2FA backup codes? Because in like 4 years, I never had to use my 2FA backup codes. You'll store your codes encrypted in the cloud, with email registered specifically for this purpose. And obviously, if you'll lose your phone or whatever, you don't try to connect from every device possible to your cloud where backup codes are. I don't know, but for me, it looks to store backup codes like that as safe as to store them on the paper.
