Please provide the following when creating the Ticket:

Game Version number: 1.2.1.169
Modded?: No (Yes/No)
If modded, please list the mods:

Issue Description: When using Legacy controller preset, clicking RB will not change firing mode if you are aiming down sights.
Using the Updated preset you are, however, using Left D-pad, able to change firing mode even when aiming down sights.
I am using a regular Series X controller.

As you can see in the video below, nothing happens to the firing mode while aiming down sights.