🤷 mountedでうまく値がとれないよォ〜

App.vue

const route = useRoute()
onMounted(() => {
  console.log(route.path) // => /
  console.log(route.params) // => {}
  console.log(route.query) // => {}
})

👮 isReady()を使ってください

App.vue

const router = useRouter();
const route = useRoute()
onMounted(async () => {
  await router.isReady()
  console.log(route.path)
  console.log(route.params)
  console.log(route.query)
})

routerが準備できていれば使用できるので、router-view内のコンポーネントではonMountedでも値が取れます