Team Win Recovery Project 3.x, or twrp3 for short, is a custom recovery built with ease of use and customization in mind. Its a fully touch driven user interface no more volume rocker or power buttons to mash. The GUI is also fully XML driven and completely theme-able. You can change just about every aspect of the look and feel.
* We are not responsible for bricked devices, dead SD cards,
* thermonuclear war, or you getting fired because the alarm app failed. Please
* do some research if you have any concerns about features included in this ROM
* before flashing it! YOU are choosing to make these modifications, and if
* you point the finger at us for messing up your device, we will laugh at you.
- Decrypt is not working for now
- Backup still have some problems use it carefully
1. Install fastboot tools from google's sdk on your PC
2. Enter fastboot mode
3. Unlock your bootloader
4. Run "fastboot boot recoveryimgfilename.img" in command line (if you want to have it permanently you should flash the installer)
5. If you will flash the installer and you are stock you need also to flash magisk or your phone will not boot again
6. Enjoy it
How to flash a custom Rom:
If you alread have a twrp flashed you can only flash the new installer zip to update your TWRP (remember to flash again magisk or your system will not boot).
If you have some problems with backup, like 255 error or something similar please check this guide: https://forum.xda-developers.com/oneplus-6/how-to/255-error-twrp-backup-restore-999-t3801632
For the Bacups use always "system_image" and "vendor_image" instead of "system" and "vendor".
TWRP 3.2.3-0 Unofficial by mauronofrio
TWRP 3.2.3-0 Unofficial Installer by mauronofrio
Thanks to @kanded
for the testing