[Vuejs]-Does Bootstrap work with vue3 or is it only working with vue2?

Pure bootstrap as a css framework is independent from vue version. Generally you can use any javascript framework with any css framerwok.

But there are libraries like:

https://bootstrap-vue.org/

where you can read:

Built with Vue.js v2.6 and Bootstrap SCSS v4.6

and on link: https://bootstrap-vue.org/vue3

With the release of v2.23.0 you can now use BootstrapVue with migration build of Vue.js 3

so support of bootstrap-vue library for vue3 is limited but in future (bootstrap-vue 3.0) full support will be provided.

There are other libraries:

https://github.com/cdmoro/bootstrap-vue-3

described as

BootstrapVue3 is an attempt to have BootstrapVue components in Vue3, Bootstrap 5, and typescript.

so you can try with this one. It has some bugs but is actively developed.