There are 3 variants of LG K20 for 3 different carriers. Among the 3 only AT&T variant has got an official Oreo Update as of now. K20 Plus (MetroPCS / T-Mobile) & K20 V (Verizon) are still on Nougat.
As K20 Plus is rootable we can get a feel of Oreo with Lineage OS 15.1 custom ROM which is based on Android Oreo 8.1.0. Even though it’s not a stable ROM for daily usage you can give it a try.
Follow the below step by step tutorial with screenshots to get Android Oreo on your K20 Plus –
LG K20 Plus Lineage OS 15.1 Android Oreo 8.1.0 Installation Guide
NOTE: Backup your internal storage before moving further as we’re going to wipe it.
The whole process can be divided into 6 Steps for ease of understanding –
Step 1: Unlocking the LG K20 Plus Bootloader
Follow this post to unlock LG K20 Plus Bootloader. After unlocking the bootloader proceed to Step 2.