Coveo implementation teams have been using Sitemap Source and Web Source to index AEMaaCS.
Coveo Product team is currently working on support for GraphQL Source. If you have ideas on improving the way Coveo indexes content in Cloud Services, to share ideas, or if you want to participate in a beta test program, feel welcome to reach out!
Thank you for the recommendation. To ensure there is technical clarity and consistency, SearchBlox AEM connector does not give access to Coveo search nor is associated with Coveo.