Can I ask how you got OxygenOS into it? I'm in China (so I believe we are both KB2000) and I want to run mine with it too.
It's simple, really. Download the full OxygenOS (EU/IN) latest zip, copy it to your internal storage (outside any folders) and from the system updater app, choose "local update" and then choose this downloaded zip. After the reboot, you will have oxygen os. And, no, you don't need an unlocked bootloader or root to do this.
PS: I would suggest EU zip over IN, as it less bloated.