Team Win has released official TWRP custom recovery for Google Pixel 2 (code named walleye) and Pixel 2 XL (code named taimen). Current status of the TWRP recovery is Alpha (twrp-3.1.1-alpha1), so it should not be installed permanently on your Pixel 2/Pixel 2 XL. However, tech-savvy users can use this alpha version of the official TWRP recovery image to temporarily boot into TWRP and play around with it.
TWRP custom recovery is one of the most popular options for flashing custom ROMs and Zip files. Since Google Pixel 2 and Pixel 2 XL are the most recent devices, a stable version of official TWRP recovery is not yet released, but a pre-release version is now available for download.
If you are interested, you can download the recovery image (twrp-3.1.1-alpha) and use it right now. Note that, you should not flash this pre-release version on your device, as it will brick your device. You can only use it to temporarily boot your Pixel 2/Pixel 2 XL into TWRP.
Read on to know how to boot your Pixel 2/Pixel 2 XL into TWRP custom recovery using the alpha version of official TWRP recovery. Note that decrypting and MTP do not work, and backups cannot be made. Ii is also unclear what a factory reset will do, so try it at your own risk.
This guide requires ADB and Fastboot driver setup on your PC (read this guide). Also proper USB driver [download here] for Pixel 2/Pixel 2 XL should be installed on the PC. Also, USB debugging and OEM Unlock options must be enabled on your device in Developer Options menu.
2. Power off your device, hold Volume down and turn on the device to boot into bootloader mode.
3. Open a command window on your PC and issue the below command to temporarily boot into TWRP recovery:
fastboot boot path/to/twrp.img