Updated koreader ...

Description is in https://github.com/koreader/koreader/wiki/Screen-saver-options. You can help by improving the description.

Platform where screensaver is an option: Kobo, Kindles without special offers, Remarkable, Cervantes and Sony.

Platform where screensaver is not supported: Kindles with special offers, Android, Pocketbook and generic linux.
Links to the description are outdated or do not correspond to the new version.
Settings -> Screen -> Screensaver.

Now awaiting your kindly help to update the wiki
PS: the wiki is the documentation. That or keeping track of github. In any case help is needed to keep things updated.
I'm glad that you noticed this and I'm hoping you'll help correct this.
deleted
Do you know if there's any chance this will be supported in the future? I'm really enjoying KoReader on my Pocketbook Touch HD 3, but I kinda miss having a book cover as a screen saver.. :/

It's not the end of the world, so if it will not happen, so be it, but it'd be nice to know if it's in the works or not..
All that's needed is a willing contributor . None of the maintainers have PocketBook devices, so it's not going to happen without external help.
After purchasing my PB Touch HD3 because my Kobo Clara HD gave up the ghost, I'm afraid I'm not in a position to donate the money needed, but hopefully somebody else is willing to be a generous donor!

In any case, like I said, it's not a major priority. I'll keep an eye out on future updates. Again, thanks for KoReader, it's been an absolute blast figuring out all the tinkering that can be done with it..
I, err, meant code contributor ;p.

Although a device wouldn't hurt, it may not necessarily be as helpful as someone familiar with how PB devices work actually looking into it: we'll gladly help with the KOReader side of things .