I had no devices that can authenticate, how do I add my devices back

If you don't have access to a trusted device or phone number, go to iforgot.apple.com. Then you can unlock your account with your existing password or reset your password.

https://iforgot.apple.com/

For the computer authorizations.

iTunes Store: Associating a device or computer to your Apple ID

Manage two-factor authentication for your Apple ID from iPhone – Apple Support (AU)

Add another device as a trusted device

A trusted device is one that can be used to verify your identity by displaying a verification code from Apple when you sign in on a different device or browser. A trusted device must meet these minimum system requirements: iOS 9, iPadOS 13, or OS X 10.11.

1. After you turn on two-factor authentication on one device, sign in with the same Apple ID on another device.
2. When you’re asked to enter a six-digit verification code, do one of the following:

• • Obtain the verification code on your iPhone or another trusted device that’s connected to the internet:Look for a notification on that device, then tap or click Allow to make the code appear on that device. (A trusted device is an iPhone, iPad, iPod touch, or Mac on which you’ve already turned on two-factor authentication and on which you’re signed in with your Apple ID.)
  • Obtain the verification at a trusted phone number: If a trusted device isn’t available, tap “Didn’t get a verification code?” then choose a phone number.
  • Obtain the verification code on a trusted device that’s offline: On a trusted iPhone, iPad, or iPod touch, go to Settings > [your name] > Password & Security, then tap Get Verification Code. On a trusted Mac with macOS 10.15 or later, choose Apple menu  > System Preferences > Apple ID > Password & Security, then click Get Verification Code. On a trusted Mac with macOS 10.14 and earlier, choose Apple menu > System Preferences > iCloud > Account Details > Security, then click Get Verification Code.

1. Enter the verification code on the new device.
2. You won’t be asked for a verification code again unless you sign out completely, erase your device, sign in to your Apple ID account page in a web browser, or need to change your Apple ID password for security reasons.

https://www.macworld.com/article/233598/how-to-add-trusted-phones-to-your-apple-id-two-factor-authentication.html/amp

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