tl;dr- The article appears to be referring to how the Media Bias Chart downgraded their assessment of Fox News to "Opinion Source" in 2018 (or 2017), which it describes as reflecting "Problematic Quality" as opposed to the "Satisfactory Quality" that the same source apparently had assessed Fox News at previously. That said, the Media Bias Chart does continue to track Fox News as a news source in the general sense, despite apparently classifying it as an "Opinion Source" in terms of reliability.
To quote the bit before the claim:
I added the NPR investigative article about tracking fake news creators so that they could see how the right is targeted with misinformation. I used the Media Bias Chart to show them where their usual news choices actually fell on the “factual and unbiased” news. I even pointed out how Fox News wasn’t even a news channel. It changed classification in 2018.
–"The Midwestern Black Professor Teaching MAGA Babies Is Not Alright"
In this context, it sounds like they're claiming that "the Media Bias Chart" stopped classifying Fox News as a news channel in 2018.
This is, they're not claiming that Fox News isn't a "news channel" in a general sense of "a channel that claims to report on the news", but rather they seem to be claiming that Fox News was reclassified in terms of reliable-vs.-fake news.
According to Google, this article from the Media Bias Chart's website is from 2018-08-29:
Fox News is now ranked far lower than the New York Times for two main reasons; one, Fox News is dominated by opinion and analysis, and two, it has gotten precipitously worse in other measures (sensational chyrons, loss of experienced journalists, hyperbolic analysis by contributors, etc.) within the last six months.
–"The Chart, Version 2.0: What Makes A News Source “Good?”"
So apparently Fox News had a higher ranking, but it fell in 2018.
This corresponding chart [PDF] shows Fox News falling in the "Opinion Sources" category, with that part of the axis labeled "Problematic Quality". Since Fox News is just barely within this category (it's almost within the "Satisfactory Quality" category) after the noted significant fall in the rankings, it'd seem that the Media Bias Chart had classified Fox News as a satisfactory news source and then downgraded it to a problematic news source in 2018.
My guess would be that this downgrading is what the article meant by
I used the Media Bias Chart to show them where their usual news choices actually fell on the “factual and unbiased” news. I even pointed out how Fox News wasn’t even a news channel. It changed classification in 2018.
–"The Midwestern Black Professor Teaching MAGA Babies Is Not Alright"
This is, the Media Bias Chart does appear to have changed its classification of Fox News in 2018, and this reclassification may've been stretched into the claim that Fox News was no longer a "[satisfactory] news channel".
This assessment appears to remain current (as of 2019-11-26):
The following scores Fox News’s overall bias and reliability scores according to our Ad Fontes Media ratings methodology.
Reliability: 23.16
Bias: 24.56
Reliability scores for articles and shows are on a scale of 0-64. Scores above 24 are generally acceptable; scores above 32 are generally good.
–"Fox News Bias and Reliability"
This is, the "Reliability" score of 23.16 is just under the threshold of 24 for being "generally acceptable".
Caveat: Unclear if this was in 2018.
When I searched for this on Google, the article I quoted above describing the fall of Fox News was listed by Google as having been from 2018-08-29, describing the fall of Fox News "within the last six months". This would seem consistent with a claim about Fox News being reclassified in 2018.
However, the corresponding chart [PDF]'s link is:
https://www.adfontesmedia.com/wp-content/uploads/2017/08/Second-Edition-News-Chart.V2.pdf
,
which includes "2017/08", which may suggest the reclassification actually happened in 2017 as opposed to 2018.
Disclaimer: This interpretation of the claim may be mistaken.
To quote it again, the claim's:
I added the NPR investigative article about tracking fake news creators so that they could see how the right is targeted with misinformation. I used the Media Bias Chart to show them where their usual news choices actually fell on the “factual and unbiased” news. I even pointed out how Fox News wasn’t even a news channel. It changed classification in 2018.
–"The Midwestern Black Professor Teaching MAGA Babies Is Not Alright"
The above answer is based on the interpretation that they're referring to Fox News being reclassified as an "Opinion Source" by "the Media Bias Chart" in 2018.
However, the article also provides a link to Fox News's Terms of Use in the claim, making another plausible interpretation that they're claiming Fox News to have reclassified itself in 2018. This interpretation is reinforced by the Terms of Use being dated 2018-10-15, which'd be consistent with the claim about the reclassification occurring in 2018.
This interpretation of the claim has already been addressed in @reirab's answer, so I won't repeat it here.