How to fit images of 16x9 aspect ratio in thumbnail without crop?

[vinser]

Hi
How do I fit images of given aspect ratio in 100vw?
For example, that's how 16x9 test image looks when is rendered with shortcode

{{< image src="img/testgrid-16x9.jpg" ratio="16x9" caption="Figure caption" class="rounded" >}}

and here how it should really look

Border radius was zeroed with

img.rounded {
    --bs-border-radius: 0;
}

as it was stated in #811
The same image crop I have for list thumbnails

Without ratio specified images are not cropped, but thumbnails are because they set them fix ratio 16x9 on lists and 21x9 on pages