I recently switched from my beloved MacBook Pro Retina (Late 2013) i5 2.6/16/512 to MacBook Pro (2017) Non-TB i5 2.3/16/512.
I purchased what from the build-quality looked like a good USB-C-to-DisplayPort cable with 4k/60Hz support, just to run into the very problem the Logicboard repair guru Louis Rossmann had described in one of his videos: As soon as you plug in the USB-C dongle, the (2.4 GHz) Wi-Fi stops working despite full antenna signal. Unplug the USB-C connector and you are immediately back in the game.
The big question I'm asking myself now: Who is to blame? Is this a design flaw in the current generation MacBooks with improper shielding or is it a design flaw in the various dongles?
I mean the fact that even Apple’s very own USB-C Digital AV Multiport Adapter is causing these Wi-Fi issues (as you can learn from the many horrific customer reviews; but AFAIK have been fixed through a software patch), show that there’s something going horribly wrong.