Step 1. Install the third party launcher you prefer. You have to install a launcher first! I chose Apex launcher from play store.

Important! If you are using gesture navigation(swipe up for home screen) instead of virtual keys. Go to Settings – Smart & Convenient – Navigation Keys. Change the settings to Virtual Key Navigation OR any gesture layout besides the FIRST ONE(Back at Both Sides).

Step 2. Open Settings – About Phone and tap on Version serval times to enter Developer Mode.

Step 3. After enabling developer mode, go to Settings – Additional Settings -Developer Options. You might need to enter a CAPTCHA to access the menu.

Step 4. Turn on USB Debugging on your Find X and download ADB tools on your computer if you do not already have them.

Step 5. Connect your phone to your computer

Step 6. Open command prompt or terminal and jump to your ADB tools folder. “For Windows users, this can be done by holding Shift and Right-clicking then selecting the “open command prompt here” option.”

Step 7. Enter the command “adb devices” and tap allows USB debugging on your phone.

Step 8. Enter the command “adb shell”

Step 9. Enter the command “pm uninstall -k –user 0 com.oppo.launcher”

Step 10. If the command successfully executed the oppo launcher should be uninstalled from your phone. Now try going back to your home screen. The third party launcher you installed should be opened.

If you wish to restore the default oppo launcher, do a factory reset of your Find X. This method will not have any impact on future OTA updates but you might need to repeat the steps after updating your system.

You can remove more oppo system apps using this method. More info please read this article:https://forum.xda-developers.com/find-X/how-to/guide-adb-oppo-x-apps-safe-to-uninstall-t3818165