[Shield Tablet Android Development] kabu0001:
First things first: i am not responsible if you brick your device. If you´re unsure about something better ask again, i´ll answer you as good as i can. Just be aware that if you do something wrong it might get really hard or even impossible to get your device working again!

Also This rom is not yet perfect. As you might have seen, Triodexe mentioned multiple times, its in an experimental state, so you might encounter some bugs. Also it doesnt include the Shield apps "Console mode" and "Accessoiries-App", so you wont be able to connect the first version of Shield controller on it, and if you connect a TV via HDMI, the Display wont deactivate or work with HDMI CEC (the Protocol which lets you controll the Tablet with your tv remote)

(Prequisites: USB Debugging ADB and Fastboot)

Download ADB and Fastboot (for windows for example "minimal ADB and Fastboot", Enable the Developer settings on your Shield tablet, and activate "USB Debugging". Then you connect your Device To your PC with adb opened, and type in "adb devices". If some long number shows up, thats your device, if not, check if usb connection is correct. And the shield might ask you if it should trust this pc for debugging. Of course you´ve got to click yes there. So when the device shows up in "adb devices", you can type "adb reboot bootloader" which restarts your Shield into bootloader mode.

(Bootloader Unlock)

If its already unlocked, then i didnt tell you anything new so far, but from your question i assume that you haven´t got any flashing experience, which means you´re Bootloader should still be locked. Luckily (for you ;D) this devices bootloader isnt locked with a key, so all you´ve got to do is type "fastboot devices" again to see if the device is connected, and then "fastboot oem unlock" WARNING THIS MIGHT FACTORY RESET YOUR DEVICE! MAKE A BACKUP BEFORE AND COME BACK TO HERE AFTER, after which the shield will show you the bootloader unlock menu. Use the volume buttons to navigate to "unlock" there and confirm by pressing the Power button.

Now that its unlocked, you can actually change something about the software (be careful, it is most times no Problem to get the Stock (original) Roms if you flashed something wrong, but most times its not the latest versions and its allways annoying, so better look twice before hitting enter)

(TWRP)

The first thing you need to install to get this Rom running is install a such called "Custom Recovery". Recoverys are basically a fallback rom which Android Devices are intendet to boot to in case of a terrible failure of there Main System, and most times there is some way to redownload the Origninal software to fix the Problem. But it is possible to flash custom versions of these Recoverys there and one of the most popular ones is TWRP. Which you can download for Shield K1 here:

https://eu.dl.twrp.me/shieldtablet/

Just select the newest Version and if its downloaded Place the .img file in the main folder of your ADB and Fastboot Program. I´d recommend renaming it to something shorter as the long names which these files come with aren´t quiet handy.

Then you Start your ADB and Fastboot Programm again, go to Bootloader Mode like First time (if you start of in Android, make sure you´re in Debug mode again (because of the Factory Reset) and go to bootloader with "adb reboot bootloader".) When in Bootloader, type in "fastboot flash recovery twrp.img" where twrp. img stands for the name of your twrp img file. Now make sure not to disconnect your device till it says "done" in the ADB Fastboot console, and then you can restart your device to twrp. Just type in "fastboot reboot" and then quickly disconnect your tablet from the computer and Hold Power and Volume Up till you see the TWRP logo. If this doesnt work for you, you can also try going into android (debugging enabled!) and type in the adb program "adb reboot recovery". That should work for sure.

(ROM INSTALLATION)

Now you can download the Rom from Triodexe on the first Page of this Thread(i recommend the zram Version, as the non Zram Version caused a bootloop for me), and you also need to Download a zip file called "Mindthegapps"(make sure to chose an arm" version, not arm64, as The Shield K1 still has a 32bit Processor which wont know what to do with a 64 bit programm), which is a packet of all Google apps including Play Store, Play Service etc. now connect your Tablet (in TWRP) to your computer and copy these 2 zips to it (it´ll show up in your File explorer like a normal android device). If its copied, on your Tablet, in TWRP select "Wipe", chose "advanced wipe" and select "Dalvik", "Cache" "System"(which will delete the old android) and "Data"(this is not your Storage or SD card, so nothing of the Personal files remaining after the Factory reset will be affected by this, to be precise, this Partition contains information like WIFI Passwords Account Details etc.) and Confirm the wipe. Then you go back to "install" or "install zips" ( i cant remember how it was named xd) and select the earlier copied Rom of Triodexe and chose to install mutiple zips. then you select the "Mindthegapps.zip" and confirm the Installation. this might take a while but when its done, you can reboot and if you´ve done all correct so far, you should be greeted by the Pixel installation Screen.

Have Fun with your renewed now Android 9.0 running Tablet, and thank Triodexe for this great Piece of work ;D (And Hope that our prayings for the Accessoiries and Console Mode App will be heard ;P)

Hope this was accurate enough to help you, if you still got questions, as i mentioned at the beginning, i´m not here every day, but if i see a question of you i´ll try to answer.