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?
You're joking, but that's how I unintentionally use the web with Arc Browser. It has rounded corners and an adjustable sidebar of tabs on the right left*. The resulting viewport is tightly approximately* 4:3.
Iirc, Edge can also have tabs on the side.