The engines section in package.json claims:

  "engines": {
    "node": "^12.20.0 || ^14.18.0 || >=16.0.0"
  },

However, the helpers file uses nullish assignment operator ??=: https://github.com/un-ts/napi-postinstall/blob/main/src/helpers.ts#L71

Together with tsconfig target set to ES2021, this package is currently not compatible with Node versions below 15: https://node.green/#ES2021-features-Logical-Assignment-----basic-support