How to disable Firebase backend?

[vivami]

I'm trying to get the tech-radar running locally without the Firebase functions (not planning to use them). I've loaded up a Contentful instance with the example contentful-export-2022-04-18.json and populated the REACT_APP_CONTENTFUL_ACCESS_TOKEN and REACT_APP_CONTENTFUL_SPACE_ID in .env file (renamed from .env.example. Both the front-end and back-end run without error, however, when loading the page on localhost:3000, I get the error

Firebase: Error (auth/invalid-api-key).

How can I try out the tech-radar without setting up Firebase etc.? Thanks a bunch in advance!