line on the screen without any physical damage

Unlikely to be related to the update. Take a screenshot by press and releasing either Volume Button and the Power Button. Review the screenshot but in the opposite orientation (landscape). If it appears in the screenshot, this would indicate a software bug. That can be fixed with a Forced Restart. Force restart iPhone - Apple Support

• Press and quickly release the Volume Up Button
• Press and quickly release the Volume Down Button
• Press and hold the Side Button until you see the Apple Logo

If the lines are not present in the screenshot, this indicates hardware damage. That would need servicing at the Genius Bar. Genius Bar Reservation and Apple Support Options - Apple

Updates cause thermal and electronic stress. Strong chance the screen was damaged internally during the update. It would have failed eventually this year, this just hastened tje weakness. I hope you bought AppleCare+ which is a must for such a top of the range phone as it gets older. If not, it will cost you $$

Do you have a screen protector on the device?

Remove it.

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