I had this same issue after the update as well. The following response from GrapheneOS team fixed it for me:
Try resetting Bluetooth & Wi-Fi settings via Settings > System > Reset. It's unfortunately not split up between the two so you have to clear both and add back your Wi-Fi networks. You could try using ADB to clear only Bluetooth data but we don't have time to figure out how to do that right now to give you a command. Using pm clear com.android.bluetooth may work but may not be enough.