There are multiple ways to turn the Chat function on or off in a Google Meet.

If you do not have this feature, you will need to force an update to Google Chrome:

https://support.uscsd.k12.pa.us/kb/article/369-how-to-update-google-chrome/

1.  Click on the Chat icon on the top right of the screen:

2.  Click on the button  "Let everyone send messages" to turn the Chat on and off.  You can turn it off and on multiple times during a Google Meet. 

OR

1.  Click on the 3 dots in the bottom right hand corner, then click on Settings.

2.  Click on Host controls and use the button to turn the Chat function on and off.