When you're on the Google Images page scroll all the way to the bottom. There is a choice there to use either Google Tablet or Classic (defaults to tablet on the iPad). Click on classic and you should get the same options as on your mac/pc.

Press & hold the camera control button to open Visual Intelligence. Tap the shutter button to take a picture. The Ask button on the left sends it to ChatGPT. The Search button on the right does a Google reverse image search.

In the Google app you can use Lens and select a photo from your library. You need to tap the Lens icon and then tap the Photo icon next to the search button.

I completely agree with Othabit. It isn't that hard to understand that an iPhone or iPad user should be able to use reverse imaging search from the phone, without having to upload the picture to the computer. For example: a few days ago I was on a hike with some friends and we came across a strange plant of which I took a picture. I then tried to do a google reverse imaging search which I couldn't do because it is impossible with an apple devise. My friend with android was able to do it right there on the spot and we were able to identify the plant. It's little things like this that keep making me want to switch devises.