Overview
I will try JWT authentication, referencing the following article.
https://www.drupal.org/docs/contributed-modules/api-authentication/jwt-authentication
However, after trying it, it appeared that a paid plan subscription was required to use JWT authentication, and the investigation stopped there.
Prerequisite: Download and Installation
Install and enable the following two modules.
https://www.drupal.org/project/rest_api_authentication
https://www.drupal.org/project/restui
Steps to Configure JWT-Based API Authentication
Follow the instructions below to enable the API and set up JWT-based API authentication.
However, at the point of selecting a method, as shown below, it appeared that selecting JWT required subscribing to a paid “Premium” plan.
Summary
Since the investigation is still ongoing, the information may be inaccurate, but it appears that the following module exists for JWT authentication:
https://www.drupal.org/project/jwt
Additionally, the following module appears to be available for using OAuth2:
https://www.drupal.org/project/simple_oauth
Next, I will investigate how to use the above two modules.