I can't seem to filter the submissions by Linux support any more. I'm pretty sure you used to be able to. In the "Filter" box there's Windows, Mac, and even Android but not Linux. I assume this was introduced as part of this update, and is simply a bug or oversight.
Edit: For anyone wanting to rate Linux games having this problem, a work-around is to use the randomizer, which _does_ have a Linux filter, and as a bonus, can use multiple filters at once. Actually it'd be nice to have that functionality on the main list, too.