From the help center (emphasis added by me):
Questions that you may ask:
- Using and administering official Ubuntu flavors including: Edubuntu, Ubuntu GNOME, Kubuntu, Ubuntu Kylin, Lubuntu, Mythbuntu,
Ubuntu Studio, Xubuntu and Ubuntu Touch.
- Running third-party applications on Ubuntu.
- Development on Ubuntu.
- Services provided by Ubuntu
- Any question not mentioned below or here are great!
So, there are two possibilities:
- Since KTorrent is provided in official Ubuntu repositories, you may consider it part of Ubuntu and questions about it as questions about how to use Ubuntu. Then under the first bullet point, the question is on-topic.
- You might consider KTorrent sufficiently niche that it is in effect a third-party application. Or you may construe what is Ubuntu and what is a third-party application very broadly, so that most apps people run on Ubuntu, even most of those provided in the official repositories, are third-party apps. In that case, under the second bullet point, the question is on-topic.
I should perhaps mention that involving the use of some part of Ubuntu or third party application does not ensure with 100% certainty that a question is on-topic. "How to write compelling action heroes in the novel I am composing using LibreOffice?" would surely and swiftly be closed. But this question is asking directly about KTorrent's core functionality. It's on topic.
Of course, none of this speaks to the quality of the question. (I think it's okay with respect to quality, scope, and so forth as well, but that's a separate matter which you haven't asked about.)