Query Form Submissions in custom Admin Listing page

Sure, you can do anything!

There's an example in the Kentico Community Portal of a widget that lists form submissions. This could be adapted to display that same information in an Administration UI listing page.

This widget displays submissions from a specific form. If you wanted to create a listing that showed results from any form you'd need to do more work to make it dynamic.

Take a look at the source (F12 to decompile in VS Code or VS) of the listing page for the Forms application's submissions list. You can find the names of all pages in the administration UI. This will give you a good starting point to work from.