We had the same problem. Svelte would have been perfect if it only had a true SPA router. SvelteKit is too complicated for a simple SPA.
Still, I'd give try, it looks like people are still using it, and perhaps someone else will pick up the burden of maintenance, since there's clearly a ton of demand: https://github.com/EmilTholin/svelte-routing/issues/236
but it's not official, and Svelte project seems careless for client routing, instead it tries to convince everyone use its SSR-first kit, that "can do CSR too", which means you have to carry the whole SSR code base and its documentation into your CSR project totally unnecessarily.
I get it Vercel needs SSR for its business, I don't get it why it keeps selling everyone that "my SSR-first framework is great for CSR SPA too", it is NOT, not at all.