Just a quick google with set to since last week reveales a lot of people are complaining about the Switch not working propperly on HDMI..
TV's that won't display a signal, Failling HDMI ports, Intermitted signals...
Reports of some people get it fixed by updating the software of the switch..
Elgato seems to get a capture running in 720P but not on 1080P.
Since the Switch is just 1 week on the market and so many reports of HDMI problems.. I would wait and let it settle a few weeks to get a update out for the Switch to get things right.. But also go complain at the nintendo forum if you not already did this.. Because if many people complain about it.. They should fix the issue right?
It sounds to me that the switch has a serious EDID malefunction.. So this could be the reason that the BMD cards go in NTSC or 480....
What you could try is to put a HDMI splitter between the Switch and TV. Let them connect an play so the edid info is running 1080 or 720 or whatever... Then connect the capturecard and see what happens..
If you have to buy a HDMI splitter i would recommend one with EDID manegement like this one for 50 dollars
https://www.marmitek.com/en/product-det ... 12-uhd.php