On 11/13, the way you associate sales activities with your deals is getting a major upgrade. In this article, we'll walk through the why and how of the change.
Is it possible to make particular setup or change Deal activity View to get back the old behavior (show activity log of all associated contacts, not only activities associated with a deal directly) ?
It’s not currently possible to revert to the old activity association, and I’m not aware of any plans to change the way activities are associated to deals. If you have the inclination, I would encourage you to check out the Ideas Forum on the HubSpot Community. There, you can create a post including your use case that product and other customers can see.