pusser why have they turn the GD into a duel forum. On the old forum if you posted anything that had even a vague resemblance to another forum, a staffer would move it!
It is one of the features of Flarum which has not yet got a work around. There are no separate forums or groups like we used to have; just discussions with different tags to indicate where they belong.
Unfortunately, it is currently not feasible to have a separate tag for every different feature which used to be a group on the old platform. When you look at All Discussions you see a column giving you choices. You will see the various Tags if you choose the Tag option ~ they appear as boxes with the content within the box, and you can then choose which tag you want to look at. But the page is already filled with boxes before they divide it still further.
Using the suggested ‘hiding’ for the sub-group of Forum games (instead of ‘following’ or ‘not following’) will hide the games from your All Discussions and GD discussion threads. If you want to see games you can click on the sub group in the list, and just those posts will show.