[shamanNS]

@Sirtel I used it also with stock Kobo software, tried both epub and kepub files. Also tested reading for 1 hour with stock vs 1 hour reading in KOReader and both are quite similar in terms of battery discharge). Reading experience with KOReader is to my habits and expectations significantly better that even if KOReader would drain say 15% more battery (and it doesn't) than Kobo stock software I would still choose to use KOReader.
I've tried "patched" stock Kobo software and still dislike it overall (even "patched" Kindle PW3 was more to my liking).

Bottom line is that for sleep / standby battery drain KOReader or no KOReader shoudn't be a factor at all, since no process is running when the device is in sleep mode / suspend or whaterver. As in KOReader is not the reason why my Libra 2 drains 3-4% of the battery for every 20-24 hours while not being used, it does the same thing if I exit out of KOReader and leave it to sleep on "My Books" tab on stock Kobo homescreen.

And it certainly doesn't have significant effect on how a Kindle PW5 behaves when it goes from running KOReader to sleep and then deep sleep state.

Battery draing while using the device to read stuff is not something that I've singled out and discusses here as a seperate issues... I've only mentioned that I can read only about 500 screens between 2 full charges on this particular Libra 2.

I haven't and problaly will never try reading even one whole book let alone read using only stock Kobo firmware for the entire time between 2 discarges. I've tested the continues use of stock firmware for 2-3 session of ~2-2.5 hours of reading and that has demonstrated always the same amount of battery discarge ... so I don't care to be 200% certain that accumulated total reading time is X or Y% different when compaired to reading with KOReader.

The main issues stands: in comparison with Kindle PW5 the Libra 2 is huge disappointment to me.
And the only reasons I still haven't sold LIbra 2 are:

1) the screen is very nice.
2) I've been "burned" 2 times already with Kindle PW5 bricking itself, and since warranty for my PW5 is tied to the US and Amazon COM if this unit would die in the near or far future I would simple not longer bother with asking Amazon for a replacement for a 3rd time!! It is to much difficulty and to much stress to organize the shipping to and from the US.

I can't really afford to keep 2 e-readers, and to have Libra 2 lying in a drawer to have just in case Kindle PW5 dies for the 3rd time. On the other hand I was very much annoyed through ~15 days I had to wait for until my old PW1 that I lent to a friend has returned to me... I now I know how much I would hate to have to wait for internatinal order to get to me. Reading on a phone is the worst...

But all in all I'm very very disappointed with Kobo Libra 2. If I were able to return it back to Amazon DE in December 2023 I would have done so... but alas..