I’ve seen #XML based formats used in multiple domains for display markup. And I always wondered: why not just use #HTML? In many of these cases HTML would work as well as the custom solution. You can restrict allowed HTML if you don’t want to bring in a full browser!
The only exception I can think of was that game company test assignment with their custom XML format resembling HTML 3.2 table markup, but with significant domain-specific conveniences, e.g. grid-like boxes that are usually achieved through #CSS (grid, flexbox, masonry) on Web Platform.
Still, re-inventing HTML is almost always a bad idea. Because this re-invention is a custom unfamiliar language that needs continuous maintenance and learning.