Using the package deployment tool in the SDK, the methods in the packagetemplate.dll are called in their expected pipeline events
BeforeImportStage()
BeforeApplicationRecordImport(ApplicationRecord app)
RunSolutionUpgradeMigrationStep(string solutionName, string oldVersion, string newVersion, Guid oldSolutionId, Guid newSolutionId)
AfterPrimaryImport()

But when the package is imported using Power Platform Admin Console these override methods are not executed.