Customize Routing Rule for Main domain and Subdomain(wildcard)

import type { RouterConfig } from "@nuxt/schema";
import { useRuntimeConfig } from "#app";
import { useRequestHeaders } from "nuxt/app";

function getSubdomain(host: string) {
  const h = host?.split(':')[0].toLowerCase();
  const parts = h.split('.');
  return parts.length > 2 ? parts[0] : null;
}

function isSubdomainRequest(): boolean {
  if (process.server) {
    const headers = useRequestHeaders(['host', 'x-forwarded-host']);
    const host = headers['x-forwarded-host'] || headers.host || '';
    const sub = getSubdomain(host);
    return sub && !['www', 'stage'].includes(sub);
  }
  if (process.client) {
    const sub = getSubdomain(location.hostname);
    return sub && !['www', 'stage'].includes(sub);
  }
  return false;
}

function transformRoutes(routes: any[], isSub: boolean, shared: string[]) {
  const isSubRoute = (r: any) => r.path.startsWith("/subdomain");
  const isShared = (r: any) => shared.some(p => r.path === p || r.path.startsWith(p + "/"));

  if (isSub) {
    const sharedRoutes = routes.filter(isShared);
    const subRoutes = routes.filter(isSubRoute).map(r => ({
      ...r,
      path: r.path.replace("/subdomain", ""),
      name: r.name?.replace("subdomain-", "") || "index",
    }));
    return [...sharedRoutes, ...subRoutes];
  }
  return routes.filter(r => !isSubRoute(r));
}

export default <RouterConfig>{
  routes: (_routes) => {
    const { ssrContext } = useNuxtApp();
    const config = useRuntimeConfig();
    const isSub = isSubdomainRequest();
    return transformRoutes(_routes, isSub, ["/about"]);
  },
};

pages/
   - index.vue // maindomain
   - about.vue // maindomain
   - subdomain //subdomain folder
      - index.vue

routeRules: {
  "/": { ssr: false },
  "/about": { prerender: true },
  "/**": { ssr: true } // transformed subdomain routes
}