Invalid phone number while creating Apple ID

I've seen numerous threads on this topic that have all been closed, but none with good solutions other than calling Apple Support (a not-so-good solution by my own experience).

Problem: Setting up an Apple watch for a child with a standalone account (i.e. not associated with an iPhone plan), when upon submission of my phone number as a recovery number, an error message that reads "Invalid Phone Number" presents and forward progress on setup is ended.

After 4 grueling days of troubleshooting with Apple, then my cellular service provider, it was the latter that recommended that, at the stage of Apple ID creation in which a phone number is requested, deleting the pre-populated phone number (my own), re-typing it in, then submitting it. This worked, and I hope it works for anyone reading this.

Apple, you have to fix this ridiculous issue. Your system pre-populates the correct phone number, but whether there iis additional hyphens, whitespace or something else, it leads to a failure that is incorrectly blamed on the cellular service provider.