If there is any rule comprising of even a single unsupported component we exclude that rule from export and highlight in our Requires_Attention report. Additionally these rules are accounted for in Summary report as well (in Not migrated column for Post-Migration Summary report and in Expected not to migrate column for Pre-Migration Summary report)

In the error report, we should provide a more descriptive error than "This rule isn't supported and won't be migrated"

Provide a description of the particular Component that is not compatible based on public docs: https://support.atlassian.com/migration/docs/how-to-migrate-automation-rules/