The +86 gap in the support form is a known pain point for Chinese developers. A few paths worth trying:

1. Go directly to https://support.github.com/contact and try "Account security" or "Account access" as the category. Some flows in that form offer email-based verification instead of SMS. The category you pick affects which verification method gets offered, so it is worth trying a couple of different ones.

2. If you have any way to use a phone number in a supported country (a VOIP number, a colleague abroad, Google Voice if accessible from your location), you can use it just for the one-time code. The number does not stay associated with your account permanently.

3. Email support@github.com directly with your username (ssssssssseee), a brief description of the flagging incident, and a note about the SMS deadlock. Some people have gotten a manual review path opened this way.

This forum has no access to account management tools, so no one here can resolve it directly. That said, GitHub staff do read these discussions, and calling out the +86 issue specifically may help get visibility on it.