.wp-block-gallery.is-scroll-gallery {
	overflow: hidden;
}

.wp-block-gallery.is-scroll-gallery.keen-slider {
	display: flex;
}

.wp-block-gallery.is-scroll-gallery .keen-slider__slide {
	flex: 0 0 auto;
	width: auto;
	max-width: 320px; /* adjust to taste */
	min-width: 0;
}

.wp-block-gallery.is-scroll-gallery .keen-slider__slide img {
	width: 100%;
	height: 100%;
	object-fit: cover;
	display: block;
}