Try this

import pluginNext from '@next/eslint-plugin-next'

export default defineConfig([
  {
    plugins: {
      '@next/next': pluginNext
    },
  },
  {
    files: ['**/*.ts', '**/*.tsx'],
    rules: {
      ...pluginNext.configs.recommended.rules
    }
  }
])

Type error: Cannot find name 'x'

That's not an ESLint report. That's a TypeScript report. Your whole investigation is going down the wrong path.

ESLint and TypeScript are both tools that give feedback on your code without running it (this is called "static analysis"). But they're two very tools:

• ESLint runs a configurable set of individual rules, many of which can be loaded in by plugins such as eslint-plugin-next
• TypeScript is a general-purpose type checker that reports when the way you use values in code mismatches its understanding of what's available to be used + how (the "type system")

Any report starting with "Type error:" is a TypeScript type error. The way to suppress TypeScript type errors is with an inline // @ts-expect-error (preferred) or // @ts-ignore (less preferable). See https://www.totaltypescript.com/concepts/how-to-use-ts-expect-error for a good explanation.

Aside: instead of suppressing the TypeScript type error, it would be better to tell TypeScript about x existing. That way it can give dev-time assistance for x & let you know if you're using it wrong. https://www.typescriptlang.org/docs/handbook/declaration-files/by-example.html has docs. For example, to declare x as a constant object with a .constructor:

declare const x: {
  constructor: typeof Object; // or typeof whatever class
}

https://www.typescriptlang.org/play/?#code/CYUwxgNghgTiAEYD2A7AzgF3gDwFzwG8AoeUxVTGAVzAyRnwwE8AHEJAM3gHkAjAK3AYA3EQC+ooihAB3HADpk6DNVr0AFAEphQA

Not that much really. Maybe these links help you:

• #37151
• #52845
• #78679