There are no cooperative apartment shareowner forums that are active that i know of. I believe this is due to the shareowner not wanting to screw themselves by broadcasting the problem and being unable to sell. This has enabled the problem to stay hidden in plain sight. I and many others have written New York Attorney Generals office for help in enforcing the financial transparency of the coop apartments, with zero assistance. I have only found two resources for coop apartments, both mainly for boards,but their is still info there for shareholders. Each has published at least one of my questions. Same with the New York Times real estate section in their coop-condo Q&A, and all in their print editions. The cooperator and the habitat magazine are the coop-condo monthly publications.
I have made a post on redditt to see if i can find any help there.