Is there something that needs to be set for the Sonnb redirection to take place? Perhaps I am not understanding what exactly should happen automatically.Did you import sonnb's gallery first and retain the content IDs?
If so, the URL structure is almost identical (with an additional bit of code that covers the "photos" route, IIRC) so the redirection actually should happen automatically if you retained the same IDs. If you didn't do this, unfortunately you'd either need to do the import again, or look for some other custom coded redirection solution.
I did an import, retaining the old IDs, but no redirect is taking place.
Old URL: https://coolscifi.com/gallery/photos/kurt-miller-art-gallery.3836/
New URL: https://coolscifi.com/media/kurt-miller-art-gallery.3836/