Usually, these local sellers can be found on social media to offer their services to friends or other people.
I can't think of anywhere worse to find a peer to peer trading partner than social media. The signal to noise ratio on platforms like Facebook or Telegram is heavily skewed towards "noise". These platforms are absolutely rife with scams.
I have a solid experience in this. Back in the day, there was barely any place where people can buy/sell Bitcoin from Bangladesh. As a result, Facebook was the only source to do so. I was an admin in a Facebook group (cryptocurrency discussion). I used to get scam accusations almost every day. It was a surprise that people get scammed and again looked for deals on Facebook. There were different kinds of traps around which made face-to-face deals risky too.
Well, later I introduced escrow service there and it was running smoothly + generating good profits for me until Binance came up with their shit idea.