I hit upon this combination by accident recently. I bought a used Icarus Illumina HD, e-ink 300dpi 7.8 inch screen 4x3 aspect ratio, Android 4.2.2 via E-bay. fwiw the Icarus and the Boyue t-80 are essentially the same device.
Sadly Android 4.2.2 is not compatible with current Google Docs and it's not good with most Bluetooth version 4.0. I did find some workarounds though.
I also happened to get a very good price on a Brydge Mini keyboard, an aluminum bluetooth keyboard with backlight, built expressly for the Apple Ipad mini 4.
The Ipad Mini4 slides into a pair of clips on the back of the keyboard and allows continuous tilt of the keybo.ard to 180 degrees.
It turns out that the Boyue/Icarus e-reader and the Ipad Mini have very similar dimensions. The Icarus is slightly wider, a little shorter (a couple millimeters), and more or less the same thickness. It's not a perfect match, but it's good enough to allow me to close the Icarus over the Brydge keyboard when I'm not working. If you're OCD about everything ining up just right, you won't be happy, but if you're flexible and just want something that works, it's a surprisingly functional match.
The bluetooth paired pretty easily though some of the keys are IOS only. Still the ones most of us type with map just fine, including the volume up and down keys and the backlight. Together the devices weigh about 19 ounces.
I found that Jotter Pad will synch with Google Drive, but it does limit you to working with .txt files on the E-reader. Kingsoft Office also works, but synching is a little tricky, because it tries to save files locally instead of on the cloud. On my desktop (Linux), I edit the files through Google Docs, export as a txt file, and put the exported file back in google cloud to replace the original txt file for jotter pad (not exactly fun). On my chromebook, Calmly Writer works very well for reading and editing the same txt file from google cloud. I use a screen rotation app to keep it in landscape and bluetooth always on.
I can take the device outside and write in full sunlight, use the bluetooth for spotify (surprisingly it works on the Icarus) for background music, and type surprisingly comfortably. fwiw an 8 inch keyboard is pretty cramped, but Brydge did a really great job with layout and feel. IT's also quite fast going from keystroke to android. Unfortunately, e-ink carta simply doesn't do screen writes all that fast, but it's definitely good enough. It also helps to have a non-folding keyboard. I find that it's easy to find places to sit outdoors, but it's not always easy to find a flat surface to type on. The Brydge works very well in my lap.
There's a similarly sized e-reader, the Inkbook Explore, that's coming out soon that runs Android 4.4.2, which means that it should work with google docs natively. It's supposed to be about $195 U.S. You can get a used Brydge Mini keyboard for under $20. AS a device, the screen's better than most dedicated e-ink typewriters and it's also more flexible. I can do Pocket, google calendar, overdrive audio books, spotify, Kindle, etc. on the device in addition to writing. While the fact that I wouldn't keep attaching and detaching the reader from the keyboard (I don't completely trust the clips) is a drawback, the right arrow key happens to work as a page turning button when I use it as a reader and the keyboard serves as a stand when I use it for reading. One other caution, when you use an e-ink device as a table instead of as a reader, the battery life becomes dramatically more tablet like, it may even be a bit worse than a comparable LCD tablet. You won't get alpha smart or kindle paper white life out of the thing.
https://drive.google.com/file/d/1BLgDOHu8oJcWrejHZr66kTkCTQVyOiPt/view