OBS Studio Decklink Output not working

[miagg]

Sadly OBS 30.1.0 released two days ago and it does not include a fix. I'm pretty convinced the common denominator is ffmpeg which is used to output to those devices. So, no 4K output at the moment.

 

[gheedough]

So I've been trying to fix this issue all day (we're using Macs and UltraStudio Mini 4K) and the 4K output comes from the DeckLink Output just fine - it shows on the monitor of the US4KM, and I can pull an HDMI out directly from the unit and get it to display the output I'm mixing in OBS.
What DOESN'T work is the vision mixer (ATEM 4 M/E Broadcast Studio 4K in our case) - when I try to route the SDI output from the US4KM to anywhere else (Teranex, TV monitor out, etc) it's just black.