All the migrated channel messages are appearing with the migration account name instead of the original user.
This behavior is by design and is due to limitations within the Microsoft API. Specifically, the Microsoft API restricts certain aspects of the migration process. As a result, during chat migration, the content will be migrated under the Migration account and will appear as if it were migrated on behalf of that account. This is because of the way the Microsoft API handles permissions and identity during the migration process.
Please take a look at our User's Guide under the Teams Migration - Migrate Chats.
