Has anyone outside the U.S. successfully managed to enter their Foreign TIN in this form?Yes.
Did you just enter your local tax ID as it appears in your country?
Yes, I'm have 10% withholding rate.
Or did you need to contact support and provide additional documentation?I didn't have to submit any additional information or documents; I simply filled out the online application form.
I can't remember exactly which options I selected (I just checked, but I don't have any record of the interview values), but it is possible to enter your FTIN in some point. Read each option carefully; sometimes the wording can be misleading, and it's likely you may have selected an incorrect option at some point.