Fivetran offers four data loading methods when a connector is not available for a specific source: file replication, webhooks, database applications, and cloud functions. File replication involves converting data into files that can connect to the destination using one of Fivetran's file replication services. Webhooks send data from applications that support them to the destination. Database applications require an underlying supported database for connection. Cloud functions allow users to code custom data connectors as extensions of Fivetran, while email connectors generate an email address for sending supported file types for ingestion.