Hmm... Not saying you're wrong but have a look at https://beehaw.org/post/477824 for example, it definitely seems like sorted By Recency
Edit: actually, it's the same as the Web UI, which clearly says Hot, so I guess the answer is indeed Hot but the Hot algorithm prioritizes recency?
Good news folks - looks like comment sorting is on the way based on this pull request!
https://github.com/dessalines/jerboa/pull/495