Its provided by Google Lens suggestions, so you'll need to have that enabled in the Camera settings for it to appear. It also seems a little slow sometimes, give it a few seconds for it to show up a small suggestion bubble at the bottom of the viewfinder.
I'm using Google Camera version 8.1 on a fully updated Pixel 4a and it works for me.
I'm using Google Camera version 8.1 on a fully updated Pixel 4a and it works for me.