My paranoia about my devices stability and its 2FA software (LG G4 bootloop victim) means that I keep two phones with 2FA verification and applications enabled - one stays safe at all times so that in case I lose or drop my new one I can use the backup.
I've lost my phone and been able to re-connect to every 2FA service I use without any need for human interaction. For google I was saved because my laptop was still logged in and I could turn google's 2fa off.
Basically everyone else has an "I lost my device" thing and a fallback to SMS codes or email links. This certainly weakens 2FA in general, but strict 2FA is unusable in practice.
Just store your 2fa totp key or qr code or backup somewhere that is either protected by 2fa (password manager, online storage) , or is available offline (file cabinet).
Some online storage services have secure areas requiring 2fa to open which would be suitable.
Most services that use standard TOTP codes have backup codes that you can print out and store in a safe, and the ones that don't you can save the QR code that enrolls the 2FA app and use it again to re-enroll a new device if needed.
Obviously the backup codes are preferred as you're not storing a master key to all future codes, but it's a lot easier to manage than a second device (at least for me).
