What you want to do is already baked into WordPress but just not frequently used.
In either the classic or the block editor, click to add an image.
Once you have the block upon, instead of uploading or pulling from existing images in your Media Library, click on Insert from URL.
Now just paste the URL from wherever the image is being served. Just double check and make sure that you can hotlink images from Google.
UPDATED WITH GALLERY METHOD:
Adding externally hosted images to the gallery requires a bit of a workaround though... ...you'll want to have a few 'placeholder images' in your media library. Start by adding those placeholders into a gallery, then you'll edit the block in HTML and replace the URLs for your placeholders with the URLs of the externally hosted images.
So I used the standard WP method to add images to the gallery.
Next I click on the three vertical dots to "Show More" Block settings and choose Edit as HTML.
Once I see the HTML I do a few things, I clear out all of the extra stuff, like the class that specifies my placeholders attachment ID and anything else I feel I won't need. But really the most important thing here is that I changed the
src attribute for the image by pasting the URL of the externally hosted image. I did this for both images.
Then I switch back to Visual Editing using the "Show More Settings".
In the Visual editor you can see that both images are now visible. I then update/publish/save as draft and when I view the front end of the site... ...voila!