The approach that I did in an online course that I co-taught was actually an idea by the friend with whom I was teaching the class. Whether or not she was the onus for its origin isn't necessarily the point, but the way that she designed the course to still have discussion despite online contexts was fantastic.
Although this would be extremely difficult in larger classes, for smaller classes we broke off students into groups of 5 to 8 and every week we would meet on Zoom and they would have to send 2 discussion questions to the instructor the day before.
Using these questions by the students, the instructor would then lead class discussion by asking students to elaborate or posing questions to the class. This was probably the best way I had done online discussion, and in a larger class we attempted to break up students into "discussion groups" on D2L, but with over 300 students discussion was out of the question. It was way too much to grade and it would be so difficult to coordinate more than 20 Zoom sessions every week for an online class that large.
I guess an option for larger groups like that would be to have students facilitating and doing group assignments every week that require not just collaboration but discussion about the topic. But this would also backfire because students pretty famously do not like group assignments.
It's a hopeful idea, though, and there could even be situations where students could upload a video every week of the group members having a 15 minute discussion (on Zoom or otherwise, but to send in the recorded session to the instructor) in situations where the courses are large. Discussion is difficult to facilitate in face-to-face courses let alone online, and is particularly difficult in large courses.