Overview
I tried GraphQL with Drupal, so this is a personal note for future reference. The following document was helpful.
https://drupal-graphql.gitbook.io/graphql/
This assumes Drupal installed on Amazon Lightsail.
Module Installation
Install the following module.
https://www.drupal.org/project/graphql
However, it was necessary to install the following module beforehand.
https://www.drupal.org/project/typed_data
As a result, the installation was completed with the following commands.
Module Installation from GUI
I checked all three related modules below and installed them.

Configuration
Access the following URL.
/admin/config/graphql
Under “Create server”, I configured it as follows. I named it test_server.

Explore
Access the following URL.
/admin/config/graphql/servers/manage/test_server/explorer
You will be redirected to the following screen.

Let’s try the following query.
The following result is obtained.
Summary
In the future, I would like to investigate usage methods with custom schemas as well. I hope this serves as a useful reference.