Well technically in any *.js/*.ts file, but my 🧠 just got stuck on "this has to be part of ember-template-lint config", because I've seen a component that is basically just HTML.

At the end of the day, the linter rule is about JavaScript classes.

So if anyone bumps into this, the answer is NOT to put the config in .template-lintrc.js, but to eslint.config.mjs (or equivalent), in following way:

// eslint.config.mjs

export default ts.config(
  {
    files: ['**/*.{ts,gts}'],
    languageOptions: {
      parser: ember.parser,
      parserOptions: parserOptions.esm.ts,
    },
    extends: [...ts.configs.recommendedTypeChecked, ember.configs.gts],
    rules: {
      'ember/no-empty-glimmer-component-classes': 'off',
    },
  },
);