First, am I correct that if I use the available until feature for setting up my discussions then students should still be able to view such discussions after said date, but will no longer be able to post to the discussion?
Second, when I have been using the availability date feature, my students who access Canvas via my school's web link are able to do just that, i.e. they are able to see past discussions in their entirety (their own posts as well as those of their fellow students etc.). However students using the Canvas Student app on their phones or their iPads get the message "This topic was locked" and the date and time I used for the availability feature. When I view the course as a student I have the same result (i.e. when I use the campus link, I have access to closed discussions, but when I use the Canvas Student app I do not).
When I remove the available until date, the discussions unlock and students can see the previous discussions.
I know I can work around this problem (e.g. by not using the availability dates and then closing the discussions for comment manually), but I was wondering if I was missing something obvious or if it is a limitation of the app or a bug or something else. Thanks for your help.
I do not think you are missing a step that would address this. You might want to suggest viewing discussions that have already ended through the student app as a feature idea here: https://community.canvaslms.com/t5/Idea-Conversations/idb-p/ideas