Looking past the "nomads were an idealized version of our own society" lede, ancient DNA is very cool. A good place to follow news is Razib Khan's blog. It's also exceptional that a high percentage of the constantly-growing data is conveniently made available in one place by the David Reich lab:
Scholars use the modern Mandarin reading of the Chinese characters in question, because the Xiongnu did not leave behind their own name. Even the affiliation of the Xiongnu language is unclear, with competing hypotheses. For similar groups where we do have an endonym or at least some non-Chinese name (e.g. the Khitan or the Tabgač), then that non-Chinese name is used.
Yes, I can read Wikipedia. In fact I wrote my comment precisely because I have.
> Scholars use the modern Mandarin reading of the Chinese characters in question
You are telling a half truth. They are using modern Mandarin reading based on old Chinese characters that themselves were originally chosen based on how the actual name of this culture sounded at the time. In other words, you can pick any vaguely similarly sounding word in Chinese or otherwise and it'll probably be true to life enough and without the unnecessary slur.
FWIW, I wouldn't recommend Wikipedia as a source: I’m familiar with the actual research into what language the Xiongnu may have spoken, and I have known some of the scholars involved personally. I must say I have never heard any concern whatsoever about the term Xiongnu being offensive. First of all, this niche of linguistics is mercifully free of the outrage culture found on social media or among academics in certain, mainly native-anglophone countries. Secondly, the Xiongnu are all dead by centuries, and people are hardly going to consider possible offense when there are no (agreed) modern representatives of the group. There are quite a few ethnonyms around that were originally pejorative, the Xiongnu are not unusual in this regard.
As soon as agreement is reached on what language the Xiongnu spoke, and it happens to be a language we know enough about, it may well be that Xiongnu will be replaced by a phonetically more precise reading, just like other groups. Meanwhile, who cares.
I'm being facetious: not only did neanderthals die out 40000 years ago, but they're named after the Neander valley where the first one was found. But in my opinion fretting about what we call them is as relevant to one ancient extinct group as the other.
Slavs are a extant group who you can go and talk to.
https://reich.hms.harvard.edu/datasets