If you’re wondering why your Mac’s Ethernet connection suddenly stopped working, the culprit may be Apple itself, as an the company released an update that inadvertently disabled those ports on some of its computers. The update silently downloaded and installed on Macs over this past weekend (Feb. 26 to 28), so effected users had no way to know what had caused the malfunction.
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https://www.laptopmag.com/articles/fix-os-xs-broken-ethernet-connectivity