Redox isn't Linux, it uses its own kernel. I want this one to succeed above all others, just because Rust was born to perform this kind of application: guaranteed memory safety when dealing with tens of thousands of lines of code handling hundreds of moving parts running thousands of different tasks, all at a very low level.
I'll second Plan 9, just because it sounds like scifi and truly takes advantage of how interconnected all computing hardware has become.
Third place goes to anything based on GNU Hurd. The microkernel architecture intrigues me, and I'd like to know how it effects the end user. Plus I'm just a big fan of the copyleft/FOSS aspect.
Also, I'd just like any mobile device alternative that's not AOSP, and Linux seems like a bad fit for mobile in general. Why do we need a fully-featured, all-purpose kernel when we're only gonna put it on a known number of SoCs and therefore a known set of hardware configurations? We could be optimizing the hell out of our privacy-friendly mobile OSes, but instead we've shackled ourselves to google or linux