To easily find and discover relevant information from Microsoft 365, you can use Copilot for Microsoft 365, which includes information from knowledge base articles in its responses. To integrate external information into Microsoft 365, you can create a custom Microsoft Graph connector. This connector connects to your external system to retrieve content, uses the information from Microsoft Entra ID to authenticate with Microsoft 365, and imports the content into Microsoft 365 using the Microsoft Graph API.
See the description at https://learn.microsoft.com/en-us/training/modules/copilot-graph-connectors/1-introduction
You can find PowerShell scripts to create a new custom connector and to ingest sample data here. Note you have to have a Global Admin role or the Search Admin role and an Entra ID app. To register a new Entra app, see this article at https://learn.microsoft.com/en-us/power-apps/developer/data-platform/walkthrough-register-app-azure-active-directory.