I have one board open to a large organisation called "ideas for future releases". I would like those cards to be shown in other boards with different organisations. There is one board per platform and team to make it managable. But the idea card should show up on all platform board.
I don't believe that Trello is designed to do this.
One possible workaround is to have a sort of master card on one board, and then create identically named cards on other boards, that each contain a link to the master one.
You'd have to make sure your users know to only update the master one, though, so it might be a bit fragile.