Discussions are the workhorses of online learning. They are accessible, don't require much bandwidth, available anytime, and great for students that like to take more to compose their thoughts. They're also an interaction space - the only place on Canvas where students can most material and have it be seen by the rest of the class! Here are some Discussion ideas to try this year that came out of our recent workshop:

Use it as a space for students to post work and respond to one another.
Try breaking larger classes down into small Discussion groups to talk to one another
For a robust conversation - try asking "meaty" questions that have no right answer - have students defend an opinion or connect coursework to their lived experience or real-world examples. Stress that you value substantive replies to peers as much as new topics. Save questions with right/wrong answers for assignments or quizzes.
Try a multimedia approach - ask students to post images, memes or videos in response to the week's content.
Offer regular, optional community-building Discussions. Can be silly, fun, serious, or content-related; perhaps a different question every week. Great for asynchronous classes.
Have students respond to each other with video or audio messages.
Ask students to find and post items that demonstrate a course concept: lines of text, lines of code, a video, an article, etc.
Assign students to facilitate a weekly Discussion, or small Discussion group.
For text-based discussions, consider replacing a Canvas Discussion with a tool like Hypothes.is.

Whatever you choose to try, just remember that it's really important to help students understand what you are expecting. Dividing your prompt into sections (Purpose, Tasks, and Criteria for Success) can help students understand what they're doing, why they're doing it, and what they have to do to succeed.