Beside a tricky workaround called : “Fixed aspect ratio in Figma Auto Layout (Community)”. There’s no actual way to implement a proportional image (auto-layout, artboard) resize while keeping the object aspect ratio.
It would be nice to add on top of “hug”, “fill”, “fixed” a proportional version of fill with constrained aspect ratio.
This would ease design implementation and limit the number of needed components to deliver all the different size variations. I know, it’s been posted already a while back and many times.
It also makes sense on a development point of view, as we use these techniques all the time on actual websites.