I'm using the Freesat UHD 3840 x 2160p50 signal directly fed into a Sony VPL-VW590ES 4K projector. I've had to set the video settings manually as the GB didn't want to pass in Auto. So set to 2160p, multi refresh, bt2020cl and 12 bit.
Sony info shows 3840x2160/50p YCbCr 4:2:2 and BT. 2020.
So it seems to work, but needs manual intervention to pass to projector.
And also works brilliantly through the audio visual receiver. And relief that 10m Active Optical Cable works well.
So I guess I just have to adjust the Gigablue manually?? Not that it really matters as there are only 1 or 2 Freesat 4K channels that I can get!!