The conditional exports in package.json points to files which does not exist:

This causes the following errors when importing unfetch with typescript:

Cannot find module 'unfetch' or its corresponding type declarations.ts(2307)

Also, if you're declaring conditional exports and have type declarations (d.ts) in different location, I think you need to add "types" as the first export condition (see: https://www.typescriptlang.org/docs/handbook/esm-node.html, and microsoft/TypeScript#48235)

Therefore, I believe the correct exports should've been:

  "exports": {
    ".": {
      "types": "./src/index.d.ts",
      "import": "./dist/unfetch.mjs",
      "default": "./dist/unfetch.js"
    },

FWIW, I'm using Typescript 4.9 with moduleResolution": "NodeNext"