I just put a responsive style for the Forum : it means it should adapt to any kind of display, and thus the forum should be viewable on mobiles & tablets.
You can select it from : User Control Panel -> Board preferences -> My board style -> Artodia: Phantom - Left (non left version should work as well)
If you notice anything wrong, please let me know !

Note : the tournament draws & stuff aren't responsive so it still won't work perfectly on small screens.
EDIT October 5th:
I got some issue with Google, so I had to switch all users using the previous default style to Artodia: Phantom - Left.
If you want to go back to it, select from : User Control Panel -> Board preferences -> My board style -> Prosilver_Left