When a new team is created, it comes with a default primary channel you can rename.
If you copy the primary channel of a team into an existing team with a primary channel of the same name, the copied channel will get renamed with the suffix, copied, to avoid conflicts with the existing channel in the destination.
When this occurs, you get the following tooltip:
The Primary channel was renamed to resolve a name conflict with the destination’s Primary channel
When you set up your migration, you can modify the primary channel's title in the Copy teams options.
Note: You cannot merge your source channel with the destination channel.