Techniques are described for enabling software migration and modernization services of a cloud provider network to provide completion time forecasts for various types of migration and modernization actions performed by the services relative to users' software applications. A cloud provider network provides a software migration and modernization orchestration service that helps users orchestrate the use of various software migration and modernization services. Depending on the technical characteristics of a user's application and the selection of migration and modernization processes to be performed, an amount of time needed to complete migration and modernization actions can vary widely. The migration and modernization services of the cloud provider network each train and use machine learning (ML) models to forecast an amount of time needed to complete various actions based on historical action execution data collected by the services, thereby providing useful insights into complex migration and modernization processes.