Issue
I have realized that the latest self-hosted Appsmith uses a default cloud-hosted endpoint for Oauth authorization for Google Sheet, which goes against our company's strict policy on token management. We need to use our own client id and secret to have control over the scope of the oauth. As a solution, we can connect to Google Sheet using the REST API interface instead of the native integration, but this means we will have to compose the REST API JSON format manually. There is also a feature request related to this on Github, which I will keep an eye on.
Resolution
The latest self-hosted Appsmith now uses a default cloud-hosted endpoint for OAuth authorization for Google Sheets. However, if you have strict policies on token management and cannot leak your token into a cloud environment, you can use the old way of specifying your own client ID and secret. To do this, you can connect to Google Sheets using Appsmith's REST API interface instead of using the native integration. The documentation provides a step-by-step guide on how to authorize the REST API plugin with Google Sheets.
Using the REST API plugin may require manually composing the JSON format for operations such as add, query, and remove. However, Appsmith has a feature request for a Google Sheets plugin for the self-hosted instance, which could simplify this process in the future. If you have any feedback or suggestions, you can post them on the related GitHub issue.