maybe not exactly the same, but you can achieve a glossary with views.
The "glossary mode" settings are hidden a bit beneath the "more" links in views UI, so it's not obvious how to get the desired result.
Here's an example view as an external download (as a starting point, no file upload here in the forum for security reasons).
You should be able to import the raw json via admin/config/development/configuration/single into your Backdrop. Then further elaborate the view on admin/structure/views/view/glossary_test .
Hope this helps!