vue.esm.js?a026: [Vue warn]: Failed to mount component: template or render function not defined.

found in

---> <Anonymous>

       <ElCard>

         <ElTabPane>

           <ElTabs>

             <MainContent> at src\components\admin\MainContent.vue

               <Main> at src\components\admin\Main.vue

                 <App> at src\pages\admin\index\app.vue

                   <Root>

//https://*.com/questions/45964665/vuejs-failed-to-mount-component

You might be running into the breaking change described here: https://github.com/vuejs/vue-loader/releases/tag/v13.0.0

Try adding .default to the end of your require().

component: require('./index/index.vue').default