Градиентная заливка бордера (обводки)

<style>
.box::before {
	content: "";
	position: absolute;
	inset: 0;
	border-radius: 30px;
	padding: 5px;
	background: linear-gradient(10deg, rgba(253, 174, 197, 1) 0%, rgba(18, 170, 255, 1) 100%);
	-webkit-mask: linear-gradient(#fff 0 0) content-box, linear-gradient(#fff 0 0);
	-webkit-mask-composite: xor;
	mask-composite: exclude;
}
</style>