Migrating or Moving a Channel from one Team to another Team

SW-SoCo2 Third party tools can't currently provide a 100% copy, they are limited by the available APIs that Microsoft provide. In my experience ShareGate does a good job of copying, but it isn't going to be perfect.

You could however use a shared channel, as these can switch their membership style easily. When you first create the channel uncheck the box to Share it with the Team then only the people you choose will have access

Once you are ready to make is available to all you can Share with a Team and select the team which is already where it's located, this will grant access to all the Team members now and in the future.

It's worth considering the other aspects that being a shared channel will bring, for instance having it's own SharePoint side etc.

The other option would be to just name your channel ##DO NOT USE## and make it not Shown for team members by default, people would have to go hunting to find it, I bet they'll have better things to do.