I use the OTP Auth iOS app. I store encrypted backups of my 2FA code secrets in iCloud, and also in Dropbox. I save recovery / backup codes in LastPass (whenever a service provides them.) When possible, I will set up two or more 2FA options. I always have a small Yubikey plugged in to my laptop, and some services allow me to set up a Yubikey as well as OTP codes. I also have a backup Yubikey that I set up for all the services that support it, and keep this off-site in a safe deposit box. I also store some printed copies of critical 2FA code recovery codes, mainly for my Google and Apple accounts.