That's a test of the software more than the hardware. I run a lot of stuff on low-powered hardware and the main problems are when the software allocates a ton of memory unnecessarily (Java software is usually the worst offender) or does a million things for each request that are either unnecessary or duplicate.

Any efficient blog software will handle HN fine on anything that you can call a smartphone, so like maybe not a Nokia with GPRS and 6MB on-board storage, but something like the Samsung S2 from 2011 that basically shipped as a Linux box -- just need to adb push ARM binaries for PHP and a webserver