Change record status: 
Project: 
Introduced in branch: 
10.3.x
Introduced in version: 
10.3.0
Description: 

\Drupal\Core\Extension\ThemeHandlerInterface::rebuildThemeData() is deprecated and replaced by \Drupal::service('extension.list.theme')->reset() and \Drupal::service('extension.list.theme')->getList().

Users who want to receive a fresh list of themes can use chain calling on the methods above.

$themes = \Drupal::service('extension.list.theme')->reset()->getList()

Impacts: 
Module developers