vue/no-template-key 
disallow
keyattribute on<template>
- ⚙️ This rule is included in all of 
"plugin:vue/vue3-essential",*.configs["flat/essential"],"plugin:vue/essential",*.configs["flat/vue2-essential"],"plugin:vue/vue3-strongly-recommended",*.configs["flat/strongly-recommended"],"plugin:vue/strongly-recommended",*.configs["flat/vue2-strongly-recommended"],"plugin:vue/vue3-recommended",*.configs["flat/recommended"],"plugin:vue/recommended"and*.configs["flat/vue2-recommended"]. 
Vue.js disallows key attribute on <template> elements.
📖 Rule Details 
This rule reports the <template> elements which have key attribute.
Note
This rule does not report keys placed on <template v-for>. It's valid for Vue.js 3.x. If you want to report keys placed on <template v-for> invalid for Vue.js 2.x, use vue/no-v-for-template-key rule.
🔧 Options 
Nothing.
👫 Related Rules 
📚 Further Reading 
🚀 Version 
This rule was introduced in eslint-plugin-vue v3.4.0