Node.js Typescript extension problem TypeError [ERR_UNKNOWN_FILE_EXTENSION] on different machine

Question

I created a small application as part of an employment process for a potential employer. I tried running the application locally, including on a different machine (windows laptop), and it all works. However, they are saying that they are getting an error when trying to run the backend.

Using Typescript and ts-node.

It's a little bit confusing, as I cannot seem to replicate this error on any machine I own (I don't own a MAC however, so I haven't tried that). The only way I can replicate is if I try just running ts-node src/main.ts, so without esm. In the email they mentioned specifically that they ran npm start though.

What do you think is happening? It is extra unfortunate as I cannot replicate this, so I don't know whether or not I've solved it. Check end of post to see what I tried so far.

TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for *redacted*/backend/src/main.ts
    at new NodeError (node:internal/errors:405:5)
    at Object.getFileProtocolModuleFormat [as file:] (node:internal/modules/esm/get_format:99:9)
    at defaultGetFormat (node:internal/modules/esm/get_format:142:36)
    at defaultLoad (node:internal/modules/esm/load:86:20)
    at nextLoad (node:internal/modules/esm/hooks:726:28)
    at load (/*redacted*/backend/node_modules/ts-node/dist/child/child-loader.js:19:122)
    at nextLoad (node:internal/modules/esm/hooks:726:28)
    at Hooks.load (node:internal/modules/esm/hooks:370:26)
    at MessagePort.handleMessage (node:internal/modules/esm/worker:168:24)
    at [nodejs.internal.kHybridDispatch] (node:internal/event_target:762:20) {
  code: 'ERR_UNKNOWN_FILE_EXTENSION'
}

package.json:

{
  "name": "backend",
  "version": "1.0.0",
  "description": "",
  "main": "main.ts",
  "type": "module",
  "scripts": {
    "start": "ts-node-esm src/main.ts"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "@fastify/cors": "8.5.0",
    "fastify": "4.25.2",
    "mongodb": "6.3.0",
    "mongodb-memory-server": "8.12.0"
  },
  "devDependencies": {
    "@types/node": "20.10.5",
    "ts-node": "10.9.2",
    "tsconfig-paths": "4.2.0",
    "typescript": "5.3.3"
  }
}

tsconfig.json:

{
  "compilerOptions": {
    "target": "ES5" /* Set the JavaScript language version for emitted JavaScript and include compatible library declarations. */,
    "module": "NodeNext" /* Specify what module code is generated. */,
    "moduleResolution": "NodeNext" /* Specify how TypeScript looks up a file from a given module specifier. */,
    "allowImportingTsExtensions": true /* Allow imports to include TypeScript file extensions. Requires '--moduleResolution bundler' and either '--noEmit' or '--emitDeclarationOnly' to be set. */,
    "noEmit": true /* Disable emitting files from a compilation. */,
    "esModuleInterop": true /* Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility. */,
    "forceConsistentCasingInFileNames": true /* Ensure that casing is correct in imports. */,
    "strict": true /* Enable all strict type-checking options. */,
    "noImplicitAny": true /* Enable error reporting for expressions and declarations with an implied 'any' type. */,
    "strictNullChecks": true /* When type checking, take into account 'null' and 'undefined'. */,
    "strictFunctionTypes": true /* When assigning functions, check to ensure parameters and the return values are subtype-compatible. */,
    "noImplicitThis": true /* Enable error reporting when 'this' is given the type 'any'. */,
    "noUnusedLocals": true /* Enable error reporting when local variables aren't read. */,
    "noUnusedParameters": true /* Raise an error when a function parameter isn't read. */,
    "skipLibCheck": true /* Skip type checking all .d.ts files. */
  }
}

What I tried so far is adding/changing this to tsconfig.js:

{
  "compilerOptions": {
    "target": "ES5",
    "outDir": "./dist",
    "rootDir": "./src",
  },
  "ts-node": {
    "esm": true
  }
}

and also adding these alternative scripts to package.json:

    "alt-start": "node --loader ts-node/esm src/main.ts",
    "third-alt": "ts-node src/main.ts",
    "fourth-alt": "npx ts-node-esm src/main.ts"

Do you think this will solve the issue? What is your suggestion on sending the solution back to them? If it doesn't work again... I would like to avoid that.

Thanks for the help!