I have almost the exact same issue. I bought a phone in February 2020 and exactly a year later, the screen starts to flicker. It then began to glitch, burn colours into the display, and show double of what was on the screen. It kept on getting worse and it eventually got so bad that I couldn't see anything on the phone at all. I haven't dropped it, got it soaked, or treated poorly in any way. I took it in to an authorized apple repair site at London Drugs, and they fixed it for free because I was within warranty, but they admitted it was the devices own fault. Except, 3 months later, the exact same thing is happening again, and now I'm out of warranty. Apple sold me a defective phone and they expect me to pay even more for it, as if their stuff isn't overpriced already. It really shows how much they own up to their actions.