Issue has been resolved by creating an alias for the lib in the nuxt config. See nrwl/nx#22410 (comment)

This project is a demo to reproduce an issue with the @nx/nuxt plugin (see).

I used the defaults for all prompts when creating the Nx workspace and the lib.

1. Create a new Nx workspace with the following command: npx create-nx-workspace@latest nx-nuxt-demo --preset=nuxt
2. Create a plain typescript lib with: npx nx g lib
3. Install packages with npm install
4. Run the app with npx nx serve nx-nuxt-demo or npm run serve
5. Import the lib in the nuxt server part: e.g. apps/nx-nuxt-demo/src/server/api/greet.ts
6. The following error occurs in the console:

 ERROR  [worker reload] [worker init] Cannot find package '@nx-nuxt-demo/demo' imported from /home/lmoesle/source/playground/nx-nuxt-demo/apps/nx-nuxt-demo/.nuxt/dev/index.mjs