Just wanted to let the folks at Atlassian know that one of their feedback forms didn't work.
When I disabled the Kanban backlog, a feedback form came up asking why I had done that. I filled it out, but it wouldn't submit. I tried twice.

For what it's worth, the reason I disabled the Kanban backlog is that when it's enabled, all issues on the board disappear, regardless of their status. When I disable the backlog, the board works as expected.