An open beta program has seemingly started, but you can't just get in. Instead, you need to pass an eligibility quiz. You reach this by going to Settings > System & update > Software Update then hitting the three dots and choosing Beta Program. This should work if you have a OnePlus 13, OnePlus 13R, OnePlus 13s, OnePlus Open, OnePlus 12, OnePlus 12R, Oppo Find X8, or Oppo Find X8 Pro.