Nuxt.js problematic nuxt.config.js/ts with Firebase Cloud Functions while deploying ES5/6 modules / compatibility issue

Question

I'm trying to deploy Nuxt.js (2) SSR app to Firebase Hosting/Functions. I'm able to do that, as long as I won't include nuxt.config.ts in functions/src/index.ts. However, I do have some setup there, such as meta tags, I'd like to push.

That's my nuxt.config.js file (basically default Firebase starter for .ts + nuxt imports):

const { Nuxt } = require('nuxt-start')
const functions = require('firebase-functions')
const nuxtConfig = require('./../nuxt.config.ts')

const config = {
  ...nuxtConfig,
  dev: false,
  debug: false,
}

const nuxt = new Nuxt(config)

exports.ssrapp = functions.https.onRequest(async (req: any, res: any) => {
  await nuxt.ready()
  nuxt.render(req, res)
})

Using both module.exports = { ... } and export default { ... } inside nuxt.config.ts returns:

Error: Failed to load function definition from source: Failed to generate manifest from function source: SyntaxError: Cannot use import statement outside a module

then I add "type": "module" to functions/package.json (changing package.json in root won't help) and that's what I can see:

Error: Failed to load function definition from source: Failed to generate manifest from function source: ReferenceError: require is not defined in ES module scope, you can use import instead
This file is being treated as an ES module because it has a '.js' file extension and 'path/to/my/project/functions/package.json' contains "type": "module". To treat it as a CommonJS script, rename it to use the '.cjs' file extension.

I try to change from export default to module.exports = { ... } inside nuxt.config.ts and it gives me the same error Error: Failed to load function definition from source: Failed to generate manifest from function source:...

I've tried to change to import * as nuxtConfig from './../nuxt.config' while keeping module.exports = { ... } inside nuxt.config.ts, but success either, code is generated the same, and it creates src folder inside functions/lib complicating further the structure of Firebase project.

Changing back to export default { ... } inside nuxt.config.ts and keeping import * as nuxtConfig from './../nuxt.config' returns again:

Error: Failed to load function definition from source: Failed to generate manifest from function source: ReferenceError: require is not defined in ES module scope, you can use import instead
This file is being treated as an ES module because it has a '.js' file extension and 'path/to/my/project/Doyban-Website/functions/package.json' contains "type": "module". To treat it as a CommonJS script, rename it to use the '.cjs' file extension.

Lastly, I've tried to use all import's inside functions/index.ts

import * as functions from 'firebase-functions'
// @ts-ignore
import Nuxt from 'nuxt-start'
import * as nuxtConfig from './../nuxt.config'

const config = {
  ...nuxtConfig,
  dev: false,
  debug: false,
}

const nuxt = new Nuxt(config)

exports.ssrapp = functions.https.onRequest(async (req: any, res: any) => {
  await nuxt.ready()
  nuxt.render(req, res)
})

the result:

Error: Failed to load function definition from source: Failed to generate manifest from function source: ReferenceError: require is not defined in ES module scope, you can use import instead
This file is being treated as an ES module because it has a '.js' file extension and 'path/to/my/project/Doyban-Website/functions/package.json' contains "type": "module". To treat it as a CommonJS script, rename it to use the '.cjs' file extension.

I have no idea :-(