[Vuejs]-Ref doesn't work in separate HTML template

As I understand the composition API you cannot outsource your JS code if you use it in setup: https://vuejs.org/api/sfc-script-setup.html

If you want to outsource your JS code you need to declare the component:

• https://vuejs.org/api/sfc-spec.html#script
• https://vuejs.org/api/general.html#definecomponent

Inside the defineComponent you the can hook into the setup method: https://vuejs.org/api/composition-api-setup.html