Updated Edge and it now seems to put a frame with rounded corners around every website
Edit: Looks like you can opt-out of that "new look and feel" pretty easily under the appearance settings but still, whats with putting rounded corners everywhere?
It has been for a very long time. It really ramped up when border-radius came to CSS, maybe around 15 years ago now. Every site started using rounded corners as it was much easier than the old approach of using images for it. Then apps started copying it, and now everything has rounded corners.