.env file

Where exactly is the ".env" file supposed to be located?  I tried public/, vendor/codeigniter4/framework/, and the project root, and cannot see any difference in the setting:

CI_ENVIRONMENT = development

At the root of your project at the same level as app and system.

Just 2 cents:
1. Ensure that you really have a dot in the name, e.g. it is .env and not just an env (as it appears by default in git repo)
2. Ensure that line CI_ENVIRONMENT = development is really uncommented (it appears commented by default, remove sharp char)