@nhedgehog FYI, I managed to install, and got to work on my Inkpad 2, the Coolreader version of this thread. All it took was to download and install it when connected to a different computer
Edit: I think I figured out the problem I was having - each epub that I have opened earlier on the device with the default viewer, it continues to open with the default viewer and Coolreader gets ignored. I guess the solution is to clean Pocketbook cache. This applies to Inkpad 2.
How did I get Koreader to work on my Touch HD? Well, it was a hassle, but after multiple tries and hacking it began to start up and work. It's crashier on Touch HD than on Inkpad 2, but works. It took a bit of hacking as indicated here
https://github.com/koreader/koreader...ment-268991273 (until the word powerd)
Best of luck!