Correcting tag versioning again...
This module was ported from https://www.drupal.org/project/xmlsitemap at the https://www.drupal.org/project/xmlsitemap/releases/7.x-2.2 release.
Only work related to porting the module from Drupal to Backdrop was performed. There are still several tests that fail during test runs (mentioned in the issue queue), however, manual tests of that functionality by the maintainer have passed. So, no known functionality that worked in the Drupal version of the module is currently broken.
The xmlsitemap_modal module has been removed since it worked with ctools, and the xmlsitemap_i18n module has been removed since the i18n module has not been ported to Backdrop.