How to recover Apple ID without Trusted phone number?

Just FYI, there is no recovery key with 2 factor authentication. You need at least one working trusted device, or you need to have setup a trusted backup telephone number (any voice or SMS capable number - doesn’t have to be an Apple device)

Two-factor authentication for Apple ID - Apple Support

So if you have no backup trusted SMS capable or voice telephone number listed with your AppleID, you will have to use account recovery to regain access to your AppleID. Start here - Recover your Apple ID when you can’t reset your password - Apple Support

Once you’ve recovered your AppleID, I would suggest setting up a backup telephone number especially if you only have one Apple device. It can be a VOIP number (I use a Google Voice number as my backup).

What if I can't access a trusted device or didn't receive a verification code?

If you're signing in and don’t have a trusted device handy that can display verification codes, you can have a code sent to your trusted phone number via text message or an automated phone call instead. Click Didn't Get a Code on the sign in screen and choose to send a code to your trusted phone number. You can also get a code directly from Settings on a trusted device. Learn how to get a verification code.

If you use iOS 11.3 or later on your iPhone, you might not need to enter a verification code. In some cases, your trusted phone number can be automatically verified in the background on your iPhone. It’s one less thing to do, and your account is still protected with two-factor authentication.

If you lost / can't reach the trusted device or phone number associated with your Apple ID

As long as you still have your Recovery Key and remember your Apple ID password, you can sign in and add a new trusted device or phone number to your account. You can also remove any devices you may have lost, sold, or given away.

1. Go to your Apple ID account page and enter your Apple ID and password.
2. On the Verify Your Identity screen, select "Can’t access your trusted devices?"
3. In the pop-up window, enter your Recovery Key.
4. Go to the Security section and click Edit.

Remove the device you no longer wish to use to verify your identity. If you have additional devices with Find My iPhone enabled, you can verify them as trusted devices. You can also add additional trusted phone numbers.

If you lost your Recovery Key

As long as you remember your Apple ID password and still have access to one of your trusted devices, you can sign in and create a new Recovery Key.

1. Go to your Apple ID account page.
2. Sign in with your password and trusted device.
3. In the Security section, click Edit > Replace Lost Key.

Keep your new Recovery Key in a safe place. Your old Recovery Key won't work anymore and you can't use it to reset your password or access your account.

If you can't sign in with two-step verification using your Apple ID ...

https://support.apple.com/en-us/HT202649

I am well aware of the two systems - I used 2SV for years before 2FA was developed. The OP did not say what system they are actually using - they just mention a 6 digit code and verifying their AppleID.

2 Factor Authentication uses 6 digit codes. 2 step verification uses 4 digit codes. Unless the OP was using an old device and thus had legacy 2 SV enabled from long ago, the odds are they actually are using 2FA. You have not been able to enroll a new AppleID in 2 step verification for a couple of years now, since iOS 11, so the only people still using it are those who had it from awhile ago and have not updated to 2FA yet. And anyone who was using 2SV but started using any of the advanced features in iOS 12, such as messages in iCloud, had their AppleID automatically shifted from 2SV to 2FA.

Hi Michael Black

Andyculver is talking about "2 step verification"

Two-step verification is different from two-factor authentication