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
Control Volume
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"Hey Google, volume up/down on TV."
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"Hey Google, set volume to 20 on TV."
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"Hey Google, mute/unmute TV"
Change Channel
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"Hey Google, channel up/down on TV."
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"Hey Google, switch ‘OOO (channel name)’ on TV."
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"Hey Google, return to last channel on TV."
https://www.lg.com/us/support/smart-thinq-google-assistant-voice-control#