Codename grouper
 Vendor: Google
 Type: Tablet
 Also known as: grouper
 Platform: NVIDIA Tegra 3
 CPU: 1.3 GHz quad‑core Cortex A9
 GPU: Nvidia GeForce ULP
 RAM: 1 GB
 Bluetooth: 3.0
 Wi‑Fi: 802.11 b/g/n 2.4GHz
 GSM freq: not supported
 LTE freq: not supported
 Main camera: 1.2 MP
 Secondary camera: not supported
 Peripherals: accelerometer / gyroscope / proximity sensor / digital compass / GPS / magnometer / microphone / NF
https://www.unlegacy‑android.org/projects/unlegacy‑android/wiki/Grouper_info 
PostmarketOS
compile
dpavlin@klin:/klin/pmos/pmbootstrap$ pmbootstrap install --android-recovery-zip

pmbootstrap flasher --method=adb sideload

To make pmbootstrap flasher work, I have to issue adb kill‑server on my normal terminal console so that postmarketos
 chroot can start new adb to flash device.
desktop network config
dpavlin@klin:/klin/pmos/pmbootstrap$ grep -A3 usb0 /etc/network/interfaces
allow-hotplug usb0
iface usb0 inet static
# postmarket os
        address 172.16.42.2
        netmask 255.255.255.0

dpavlin@klin:/klin/pmos/pmbootstrap$ grep -A5 pmos ~/.ssh/config
Host pmos
    HostName 172.16.42.1
    UserKnownHostsFile /dev/null
    StrictHostKeyChecking=no

reboot‑mode to reboot into recovery
https://gitlab.com/postmarketOS/pmaports/‑/merge_requests/442 
pogo pins
Top ground.
Bottom +5 volts.