Hi Josep,
Thank you for contacting Syncfusion support.
In our SfRibbon, currently we don’t have high contrast theme support in UWP. From your update, we understand that you are trying to change the requested theme to “Dark” if high contrast theme is enabled in your system or else you would like to use “Light” requested theme if high contrast theme is disabled.Can you please confirm whether your requirement is same as we stated? Based on your update, we will proceed further in this.
Regards,
Keerthana J