Apple ID recovery

Do you mean you can’t sign into your Apple ID because you no longer have the phone number it’s connected to?

If so While their online support article says for forgotten password, account recovery steps are also for a new phone number if you can’t sign in to update the number. https://support.apple.com/en-us/HT204921

FYI: Account recovery is a two phase process once started. Phase 1 is the evaluation period, usually 24-48 hours but can be longer or shorter. Once phase 1 is done it enters phase 2 where iforgot.apple.com will give you the final amount of days (can be weeks) you’ll wait. On that final day you’ll get a text, follow that text/email immediately.

See if you can recover the ID/password. Use every email address you can think of.

Apple ID - How to find your Apple    An iCloud e-mail address is an Apple ID.

Apple ID - Find              

If you forgot the Apple ID password, enter the Apple (iCloud) ID, and click Forgot Password. See if you can get a Rescue or Notification  email option if necessary.

Apple ID - Manage            

Apple ID – Forgot Password