I make a fork of meteor-svelte which uses the single version you have in package.json (and node_modules). It may not be ready for prime time, but if you are curious, try it out and see if it helps. (I also submitted a PR, hopefully Mr. Klaussner has time in the next few weeks to take a look.)
I can’t figure out where I saw it, but someone was mentioning they couldn’t get svelte-routing to SSR because it was double-mounting the routes once the client hydrated.
If you wrap your routes in a <div>, it will fix the problem.
I actually just fixed that problem (it was a silly error). The thing I’m having trouble getting to work is routing + loadable. I’m just not familiar enough with Svelte to figure out how to get the loadable thing to work in SSR code (I’m probably pretty close though)