I am not sure about the state of the firmware regarding the 2GB/8GB model, but otherwise, latest Marshmallow rooted firmware is dated 170121.
All firmware and images can be found on the Khadas Firmware page.
Khadas will need to confirm whether a firmware is suitable for your model.
LibreELEC: User balbes150 has LibreELEC versions that boot from SD. LibreELEC 8 is the latest(Kodi17).
Instructions for using LibreELEC SD images(Note:instructions will also work for balbes150’s Linux SD images).
-Down load the image and burn it to card…
Card Prep:
1.) Format an SD card to FAT32. 4GB minimum( I generally use 16 and 32 cards), Class 10 or better recommended. The faster the better.
2.) Download and extract the file, the extracted file will be an image. I use 7Zip for extraction.
3.) Burn the image to the SD card. I use HDD RAW(portable ver.). Programs like Rufus or Win32DiskImager, etc should also work. Caution with HDD RAW, make certain you select the SD card as the target, HDD RAW will write over anything… It does have a couple of confirm notices, but be careful anyway.
-To use the prepared card…
1.) With the Vim running Android, insert the prepared card (or USB flash) in to the Vim’s SD slot or use a USB card reader (or USB flash to USB).
Note: I like to use a card reader with activity LED, so I can see something is happening. The first boot can take a few minutes and the flashing LED is reassuring. 
At Android/Settings/About Device/System/updates.
From the Update and Backup App, under the UpdateLocale section, click Select, select aml_autoscript.zip, click update.
Note: Leave “Wipe Data” and “Wipe Media” unchecked/unticked. To be clear, do not use those options
-The Vim will reboot, it will do so a couple of times.
If additional info is needed, just ask.