I figured out bootstrap-vue in Vue 3 application. But it doesn't work properly, for instance, I tried to use a b-carousel, but it showed nothing.
import { createApp } from 'vue'
import App from './App.vue'
import router from './router'
import Vue from 'vue'
import { BootstrapVue } from 'bootstrap-vue'
createApp(App).use(router).use(BootstrapVue).mount('#app')