How to include externally hosted images into a gallery block

You can used this plugin Photonic for your requirement

Photonic doesn’t just cover Google Photos – it allows you to add images from a range of services.

Like the previous plugin, you’ll need to create API keys and authenticate with your Gooogle account in order to use it.

Once you do, you are ready to add a gallery.

As with the previous plugin, the photos are not added to your Media Library.

If you are not using the Block Editor

1. Click the Add/Edit Photonic Gallery button above the post editor.
   

2. Select Google Photos as the source.

3. Select Multiple Photos, Photos from an Album or Multiple Albums.

4. Filter the content if you want.

   

5. Choose a gallery layout.

   

6. Edit your gallery. For example, you may want to limit the size of the photos displayed in the lightbox.

7. Use the Insert Gallery button to insert your gallery.

8. Save the post and view it to see the gallery.

If you are using the Block Editor

1. Add the Photonic Gallery block from the Widgets section.

   

2. Click on Add Photonic Gallery in the block.

   

Phototonic provide multiple external hosted gallery

Like :

• Flickr
• SmugMug
• Google Photos
• Instagram
• Zenfolio