Получение OAuth Google бесплатно

At the time of writing, one can create a Google Cloud Identity.

Assuming you have a domain name that you can control DNS (to confirm ownership), this allows you to create Internal apps, without Google having to validate them.

I have created internal apps for Home Assistant/Google API integration that do not need re-authorising every 30 days. I have yet to pay Google a penny.

For those with knowledge of Microsoft Azure, it's very similar to Azure AD (Entra ID), which you can also create for free.