So, following the stackblitz: https://stackblitz.com/github/withastro/astro/tree/latest/examples/framework-svelte?file=README.md
I've recreated the same example with a minor change:
<Counter client:only="svelte" />
After running npm run build and trying to serve files from /dist directory, I get the following error:
[astro-island] Error hydrating /_astro/Counter.CMs1pxZ2.js TypeError: Failed to fetch dynamically imported module: http://127.0.0.1:5500/_astro/Counter.CMs1pxZ2.js