Persistent horizontal lines appear on iMac screen

You're not alone. There are many posts about 24"

iMac displays exhibiting problems:

The following topics illustrate the Silicon iMac Display problem:

Screen Failure on 24-inch-iMac, M1, 2021 - Apple Community

Horizontal Lines on Screen of iMac, 24", 2021

Horizontal black lines covering bottom 3rd of 2021 M1 iMac screen

Grey horizontal patches on my M1 iMac 2021 model

It's a hardware issue so there's no solution but to get the display replaced which, as of now, is only free is you still have Apple Care active for the iMac.

Some have quoted repair prices of around $600 US. If that is out of your budget range you might consider getting a 3rd party monitor and use it. Then if there's a recall/repair program you can get your screen repaired and end up with two screens.

Just some food for thought.

Apple has not released a recall or program so your best bet is to take the computer to your local Apple Store for repair, get it fixed and if a program is released you can request a reimbursement.

As you may know this is a user to user forum, Apple is simply the host of the forum! They do not read or participate in user to user forums so if you want to speak to Apple directly you can do so at your local Apple Store, provide feedback (don't expect a reply) at www.apple.com/feedback or call AppleCare ( AppleCare Contact Info ).

Best of luck.

Your welcome.