Hi,
When an activity is inserted into a customer journey, it can be assigned to the following three types of owners.
So you could consider to create two on-demand workflow to achieve your request.
The first one is to assign the contacts (audience) to the user/ team which you'd like to set as the owner of the activity.
And the second is to assign them back to the original owner.
Then set the journey something like the following screenshot.
After going live the journey, the activity can be assigned to the user/ team you set.
And the contact's owner will not change.
Of course, if the owner is a certain team, you can just create a workflow targeting at the Task entity and assign the task to the user/ team once it is created.
