Debian packagers: A new version of `devscripts` has been uploaded and `uscan` now supports git checkouts with submodules!
https://tracker.debian.org/news/1642515/accepted-devscripts-22511-source-into-unstable/
The online manual page is not updated yet (look for 2.25.11 or greater at the bottom of the page) https://manpages.debian.org/unstable/devscripts/uscan.1.en.html but you can see the new docs in https://salsa.debian.org/debian/devscripts/-/commit/43bff60a056e963de696f7f457c91fe4b9eb320f

Many thanks to Hugh McMaster!