Calibre Dark Mode no longer works with environment variable

Question

Setting the environment variables:

env CALIBRE_USE_DARK_PALETTE=1 calibre

and/or

env CALIBRE_USE_SYSTEM_THEME=1 calibre

No longer works, at least using version 6.3.

Answer 1

The dark mode environment variable is deprecated, and it is now moved into an option under Settings > Preferences > Look & Feel > Main Interface > Color Palette