Yes, there’s been a recent change to these:
https://github.com/discourse/discourse/pull/34081
There’s nothing to it, but fiddling around with custom css to make it work again with your specific image. (Or better yet, provide an image with a 1:1 ratio.)
Example with:
.category-heading__logo.category-logo.aspect-image {
width: auto;
height: 100px;
}
Might need some tweaks for mobile vs desktop.