SuperSU not installing on HTC One S

I am trying to root my HTC One S. The bootloader is *** UNLOCKED ***, TWRP is installed, and it's S-ON. From [these instructions](https://forum.xda-developers.com/apps/supersu/stable-2016-09-01supersu-v2-78-release-t3452703) : * I downloaded SuperSU-v2.82-201705271822.zip from the TWRP / FlashFire installable ZIP link. * I did adb push SuperSU-v2.82-201705271822.zip /storage/sdcard0/foo * I booted into TWRP and installed the above zip. Apart from complaining that /data could not be mounted (EDIT: fixed this by turning off encryption), it claims to have worked. * I wiped the cache and rebooted. Nevertheless, if I adb shell and su I get /sbin/sh: su: not found. There is a /supersu/ directory which contains su and some other stuff, but I can't run /supersu/su: permission denied. The find command finds no other file on the device matching /su$/. I also tried flashboot boot superboot.img to get Superboot, but if I do this, the device does not boot past the initial splash screen (the one saying "This build is for development purposes only..."). What went wrong?