According to LG’s website, Google Assistant works with the following models:

COMPATIBLE MODELS: WebOS 4.0 operating system only. W8, E8, C8, B8, B8S, SK95**, SK90**, SK80**, UK77**, UK65**, UK63**, UK62**, LK61**, LK54**

And you can use these commands to control the TV:

Turn Off

• "Hey Google, turn off TV."

Control Volume

• "Hey Google, volume up/down on TV."

• "Hey Google, set volume to 20 on TV."

• "Hey Google, mute/unmute TV"

Change Channel

• "Hey Google, channel up/down on TV."

• "Hey Google, switch ‘OOO (channel name)’ on TV."

• "Hey Google, return to last channel on TV."

https://www.lg.com/us/support/smart-thinq-google-assistant-voice-control#