Long story short, it looks bad. Other software uses light anti-aliasing so previews don't look pixelated. It's a wishlist report for a reason.
Please attach a screenshot showing the issue. Thanks!
Created attachment 122021 [details] Screenshot of the previews looking jagged and just bad. Pay attention to the yellow car picture.
Created attachment 122022 [details] Original image of the yellow car.
Are you using Dolphin with a > 1 scale factor, by any chance?
No sir, this is 1080p.
Oh right, this got fixed in Dolphin 19.04. Please re-open if you can reproduce the bug after upgrading to a version of Ubuntu that provides that version (or trying the Flathub version or building it from source)
Okay, sounds good. Thank you.