I'ts more Blackmagic's mistakes than yours.
Ok, I undertand. Someone lent me a SDI to HDMI 4K this morning to test if I can de-embedded the audio from a 6g-SDI. And it works.
Ultrastudio 4k mini -> SDI to HDMI 4k -> output to balance audio.
In 4K YUV 25p, no problem... but in 4K RGB (even at 25p) the signal is probably 12G-SDI and converters can't receive the signal.
Blackmagic should take more time to fix 100% of their products before to sell them. And I'm sur if they create a SDI 12G to DB25 connector they would sell it easylly.
Best
Robin
PS : sorry for my english, I normally speak french