LG never officially released Android 10 for the LG G5. The last official firmware for almost every variant of the G5 is Android 8.0 (Oreo) . Some carrier versions stopped at Android 7.0 (Nougat) or 7.1.
The LG G5 was released in early 2016 with Android 6.0 Marshmallow. LG’s update policy back then was generally 2 major OS updates. It went: Marshmallow (6.0) -> Nougat (7.0) -> Oreo (8.0). That’s where the train stopped. The phone is considered "End of Life" (EOL). lg g5 update to android 10
LG G5 Update to Android 10
The Brutal Truth about updating the LG G5 to Android 10 (Don’t get your hopes up) LG never officially released Android 10 for the LG G5