I'm trying to follow the instructions here which tell me to create credentials via the instructions here, which as step 6 tells me 'Click the user type for your app. If you're running a Quickstart, select Internal.'
On the page in question, 'Internal' is greyed out, and tells me I can't select it because I'm not a Google Workspace user. Going to Google Workspace, it tells me I need a domain name for 'my business'. Since I don't have a business, or any domain that would have anything to do with this project (I just want to push some personal data from the command line to a sheet), I don't seem to be able to proceed. Is the Google Sheets API just not available for such use?
If you don't have a Workspace account but you don't want to publish your app publicly (and go through the associated review by Google), you can set the app to External and test the app instead of publishing it.
In order to do that, just add yourself as Test user when setting the OAuth consent screen, and leave the Publishing status on Testing, don't change it to In production:
Testing
Projects configured with a publishing status of Testing are limited to up to 100 test users listed in the OAuth consent screen. A test user consumes a project's test user quota once added to the project.
Google will display a warning message before allowing a specified test user to authorize scopes requested by your project's OAuth clients. The warning message confirms the user has test access to your project but should consider the risks associated with granting access to their data to an unverified app.
Authorizations by a test user will expire seven days from the time of consent. If your OAuth client requests an offline access type and receives a refresh token, that token will also expire.