Using the Phoenix theme, you are adding channels in the Modern User Experience (MUX) to pages from Classic that aren't available yet. Your Account Settings channel displays the vertical menu from Classic if you change your language (Thus account settings page is not showing as maximized). This issue is reproducible with multiple languages including French and Spanish.
CHANNEL NAME: Account Settings
CHANNEL URL: ./../../../../niku/nu#action:personal.settings&puiFullscreen=on
Expected results: The page displays the same as it does in English (maximized with no Classic left-hand menu or top Clarity logo)
Actual results: The page no longer applies the &puiFullscreen=on setting. The Classic left-hand menu appears along with the Classic logo at the top
Release : 15.9.1 and higher
Component : Clarity MUX Blueprints and Administration
DE63717
This issue was reviewed as DE63717 and determined it will not be fixed. Instead, utilize one of the workarounds below.