$ npm ci --legacy-peer-deps
For development purpose, you can copy the template file :
$ cp public/env.dist.json public/env.json
and edit it to point to the API.
Otherwise you can set some env variables like API_HOST which will tell to the app where the backend is located.
The app will also try to find a from querystring parameters with the host of the referrer.
It will try to fetch a ${host}/env.json file. If no from param si passed, it will look on its own host.
$ npm start