Sorry that I can’t post more than 2 links, so you need search them by yourself on F-droid org - an installable catalogue of FOSS (Free and Open Source Software) applications for the Android platform.
- Kiwix Mobile
Kiwix lets you read Wikipedia and other websites without an Internet connection. It uses the highly compressed ZIM format to store webpages for quick and easy reading.
If you are not in Germany, you can download some pre-packed Gutenberg org libraries, like from this mirror
- ReLaunchX
Monochrome Launcher primarily intended for eInk and eBook devices. Can work as a system launcher or a normal app. Includes file manager, text file viewer, editor and some system functionality. …
- Gobandroid
Gobandroid is virtual goban (GO-Board) on your mobile to study and play the ancient game of Go (weiqi in Chinese, igo in Japanese, baduk in Korean).
And the related GnuGo app is in its Github repo.
- Bubble
View comic books. Optimized for tablets. Supports CBZ/ZIP and CBR/RAR. Library management with automatic bookmarks
You will need to change setCurrentItem to false in app/src/main/java/com/nkanaev/comics/fragment/ReaderFragment.java, for removing the next page animation, and compile the app by yourself.
With it you can use the notification bar to switch rotation mode. This one is not opensource but doesn’t require Internet Access permission.