An app plugin file got created: /src/plugins/vuelidate.js. We edit it:
import Vuelidate from'vuelidate'
exportdefault ({ Vue }) => { Vue.use(Vuelidate) }
Then, edit /quasar.conf.js to add the app plugin file to the build. Add this to the main plugins at the top of the file, not in the framework plugins section.