The new devices use a newer CPU. The existing nightmode hacks will not work with these CPUs. There is an update to the hack to support these CPUs. This is at
https://github.com/gtalusan/kobo-nig...r/KoboRoot.tgz.
This should work for all Kobo devices. It will be needed for the Clara HD and the updated Aura Edition 2 and Aura H2O Edition 2 devices. The latter can be identified for by a "2" in the seventh character of the serial number. For the other devices, it should work with all firmware versions starting with 4.2.8283.
Other than the update to support the new CPUs, there is no change to the hack. Installation and changing the mode works as before.
Note: I have not tested this. I do not have one of the newer devices to try it on, and do not normally use the mode at all. But, the source for the update is very reliable.