For the next day or so you can grab Hacknet - Deluxe absolutely free as the Humble Store is doing a Spring Sale Encore.
Always nice to grab a free game, especially when it will give you a Steam key and a DRM free build as well!
As for their encore sale, it's going on until May 28th. You can see all their Linux games on sale using this link as there's still plenty of decent Linux games with some huge discounts on them.
Here's a few more quick picks: