OpenRA

I can only see the original soviet and allies missions. So where are the Counterstrike and Aftermath missions as well as some custom missions from West Wood?

Not implemented yet, the entire campaign is missing at the moment except a few missions plus some handcrafted new ones.
The developers are short on manpower, so I would not expect the campaign to be added anywhere in the close future.

I saw a github discussion that some ant missions are near complete

A rough overview can be found at OpenRA/OpenRA#4989.