I stumbled on this thread and thought I’d answer for future readers. You had a baseband issue. Demonstrated by going into setting - general - about and down the bottom it should have details next to modem firmware. No details means no baseband. The baseband modem connects to the network, thats why you get searching. Fixable? Yes, by a microsoldering expert. It’s a 9/10 difficulty, so you need someone with a few years experience.