The new version 1.4.0 of the migration plugin includes plugin/theme checks for compatibility. We should revise migration instructions to mention this specific feature.
Also, this feature might be a good candidate for a how-to guide to help users understand what they need to do based on the information presented by the plugin/theme checks. A link to this guide could be included inside the plugin in a later version. Plus, the migration instructions guide would link to it too.