I have seen several posts (and have experienced it myself) that a given website hosted on Github pages looks different than the same site hosted locally. That happened to me as well. The changes were subtle. And, then I noticed the Github pages was shown at 110% magnification for some reason. When I zoomed out, the site looked the same.
For those having trouble, I also create this Svelte snippet so you can check that your local site is loading the exact same versions of resources as the hosted site.