Announcements: Course-wide messages that appear when students enter the course site and can be sent to email. They can be scheduled, and you can track how many students have viewed them.
Messages: Sent to individuals or groups within a course and appear in a feed under the Message tab. Copies can also be sent to email (currently disabled, potentially available in Spring 2025).
Dark mode is not currently available in Blackboard Ultra. However, Blackboard is considering it as a future feature. In the meantime, you can use browser extensions like the Pixie browser extension to adjust brightness, contrast, and font size for a more comfortable viewing experience.