SPMT is a decent starting point for migrating from SharePoint On-premise to SharePoint Online, especially for small to medium-sized migrations. It’s free, Microsoft-supported, and works well for basic content like document libraries, lists, and simple site structures. However, it has limitations—especially when it comes to migrating complex sites, permissions, metadata, workflows, and large volumes of data.

If your environment has customized features or a lot of content, third-party tools like Sharegate, Matalogix, or AvePoint can provide more flexibility, reporting, and smoother handling of advanced scenarios.

Another great alternative is Kernel Migration for SharePoint. It’s a powerful tool designed for SharePoint to SharePoint migrations—both On-prem to Online and tenant-to-tenant. It supports granular migration, preserves permissions and metadata, and handles large-scale moves with ease. Worth checking out if you're looking for a reliable, efficient migration experience.