Smudges (Dust) inside iMac Screen

Hi Everyone

I have a 2019 iMac and have had to get the screen replaced twice for smudges inside the corners of the screen. To be clear, these are smudges inside. Each time I take it in they 'can't tell me why' it's happening but admit it's through no fault of my own. After speaking to the tech on the phone he admitted that these devices where made with no filter where the fan is and that when it starts to take in air to cool the machine dust is sucked up and settles on the inside of your screen. I have no doubt that this will happen again, and I have raised the issue of this recurring with the folks at Apple. I'm also having issues where I hear the fan working extra hard to cool the machine down at times. I think it's an issue with dust in the motherboard and when I took the machine in they told me they would replace it. But then they said they couldn't find the part, and that it wasn't an issue.

I honestly don't know what to do anymore, and don't want to go through the bother of moving away from Apple products but don't think there is any other way to resolve this.

Does anyone have any suggestions? I feel like a lot of people are having this problem.