OK, I did contact the seller (Viofo's India distributor) for a replacement. They said they were aware of this problem and they immediately shipped me a replacement. And I received the replacement an hour ago, and everything works fine, including being able to connect the camera to my iPhone.Usually, this firmware can somewhat solve the Wi-Fi issue. But it doesn't work with your dashcam, we recommend you contact the seller for a replacement.
Thank you and everyone else here for your patience and your help.
By the way, the replacement the vendor shipped to me was a 129 Pro 4K, not the Plus Duo 2K, so I lucked out even more