Cinemachine + Timeline - Cannot cut to gameplay camera

The Timeline CM track acts as an override to the vcam priority and blending system. What you should do is put the game in the desired state as if no timeline is active (i.e. game camera active and highest priority). When you then start the timeline with a CM track, the shots in the CM track will take over - regardless of priority and whether the vcams are active or not. This way, when the clip ends, the override is cancelled and the game vcam should take over with no blend.

 

Yes. What is happening now is that when the timeline ends, control is being given back to the priority system, but the priority system thinks that the cutscene camera is the current active, and when you disable it it will blend to the game cam. If the priority system thinks that the game cam is the current active, it will take over directly when the timeline ends.

Another option is to disable the cutscene vcam GameObject, so the priority system never sees it in the first place (Timeline auto-activates vcams that it uses).