404 when migrating from Snowpack 2 "proxy" to Snowpack 3 "routes"

[Lavariet]

I tried switching from our Snowpack 2.18.4 to the current Snowpack 3.8.3 and I'm having trouble getting the proxy to work correctly.
For reference I'm using React and React-Router. If I navigate to a route using the UI everything works. If I press F5 / reload the page on the old snowpack version, the Page just refreshes, with the routes config I end up on a HTTP code 404.

My only guess as to why this happens is, in a Axios-Wrapper we wrote, we're defining a "base-path" like and this might not get picked up by routes.

const {SNOWPACK_PUBLIC_API_URL} = import.meta.env;
const path = SNOWPACK_PUBLIC_API_URL || '/api';
...
axios.get(`${path}${url}`, {params})
...

our old config had the following proxy setting:

proxy: {
	"/api": "http://localhost:8080/"
  },

I tried replacing it with

routes: [
    {
      src: "/api/.*",
      dest: (req, res) => {
        req.url = req.url.replace(/^\/api/, '');
        return proxy.web(req, res, {
          hostname: 'localhost',
          port: 8080,
        });
      }
    },
  ],

Any help is appreciated