Some gen. 1 Pixel and Pixel XL phones are seeing Google Lens pop up inside of their photos app, bringing the enhanced experience for pictures taken with the phone's camera. According to a user on Reddit who goes by the name u/LaceratedCantaloupe, there was no update to the photos app which prompted the feature showing up on their device, and it wasn't there in the beginning of the day. After some time though it ended up surfacing more towards the afternoon. With no update having happened to the Photos app, this would seem to suggest this is very much a server side thing that Google is enabling for older Pixel devices.
This seems to be a slow rollout perhaps, and after checking on a couple of devices the Lens feature was nowhere to be found. That said, that doesn't mean other users will have the same results, so if you're even remotely interested in using Google Lens at all, then it's worth checking out in the Photos app to see if it's already shown up for you. Google Lens for those that are unfamiliar is not a standalone application, but will be a feature within Photos.
Once you open up the Photos application, Lens should now be visible on certain pictures where the information button used to be. This is the little button of a letter "i" in a white circle.. While this provided some additional details about your pictures, like the file size, where it was taken with an accompanying maps image, Lens actually provides much more detail. Like information about the landmark in the photo, and you can even use Lens to look up information about a picture of a book. You can also use it to copy text, as described in the image below which is a screenshot that was shared by the user on Reddit. With this being a slow rollout, it's possible that a fair number of users with last year's Pixel and Pixel XL won't see the feature immediately, as it could take days before Google flips the switch for all users with those older versions of the Pixel lineup. Those with the Pixel 2 or Pixel 2 XL are in luck as it should be enabled by default.