If you have an Android ebook reader that’s open to installing apps, one useful app worth checking out is ReLaunchX.
It’s a free open-source app designed specifically for E Ink devices. It can be used as a file manager and as an alternate homescreen when you set it to work with the home button.
It has some additional features as well, and you can even setup the app to require using a password on the lock screen.
Most Android ereaders come with ridiculously basic file managers. Some don’t even have the option to move files, or let you choose which app to open the file with.
But then if you install a regular file manager for Android they often have fifty different features that you don’t need draining the battery on your ereader. It’s nice having a simple file manager app designed for E Ink screens.