I have tried to use swiper 6.8.0 with sveltekit 1.0.0-next.137.
I have installed swiper with npm i swiper.
There is a detailed description how to use swiper at the end of this page:
https://swiperjs.com/svelte
This is the code:
<script>
import SwiperCore, { Navigation, Pagination } from 'swiper';
/* Import Swiper and SwiperSlide components from .svelte files */
import Swiper from 'swiper/esm/svelte/swiper.svelte';
import SwiperSlide from 'swiper/esm/svelte/swiper-slide.svelte';
</script>
<!-- Pass core modules in "modules" prop -->
<Swiper modules="{[ Navigation, Pagination ]}">
<SwiperSlide>Slide 1</SwiperSlide>
<SwiperSlide>Slide 2</SwiperSlide>
</Swiper>
Result: there is no "swipe-effect", no error messages.
I have put this example to the sandbox (with svelte, not with sveltekit): https://codesandbox.io/s/frosty-engelbart-tj8ub?file=/App.svelte