He told me about John, whether he was being grilled at the border or allowed to enter the country.

Can we use "whether" in this manner ?




Yes, it seems alright to me.

Some people would insert the coordinator "and" between the two clauses.


Yes, but it's not good. When you say "he told me about John" in regular narrative, he is already telling you, so there can be no choice between versions of John's story.

 BillJ's reply was promoted to an answer.