Segue a função:

<script>
jQuery(document).ready(function () {
    jQuery(".slide-fade .swiper").each(function () {
        let swiperInstance = jQuery(this).data("swiper");
        if (swiperInstance) {
            swiperInstance.params.effect = "fade"; 
            swiperInstance.params.fadeEffect = { crossFade: true };
            swiperInstance.destroy(false); // Destroi sem remover eventos
            new Swiper(this, swiperInstance.params); // Recria o Swiper com fade
        }
    });
});
</script>

<script>
swiper = jQuery ( ".swiper" ).data("swiper");
swiper.params.effect = "fade"; 
swiper.params.fadeEffect.crossFade = true;
swiper.destroy(false)
new Swiper(".swiper", swiper.params)
</script>