From memory, to get it working I booted the j4105 with the TV in UHD mode, got the available UHD modelines via SSH, and then added them via a boot script and xrandr.
That will not give you the 12-bit Deep color modes in 4K (10-bit is not supported by GLK hardware). There is no difference how you force it to output the desired modes.
I also tried to mess around with editing the EDIDs dumped with both HDMI UHD Color On and Off to narrow down the issue.
Any 4K mode that requite the HDMI pixel clock higher than 297 Mhz give "no signal".
Intel driver does not support YCbCr 4:2:2 output. When the EDID report the max.pixel clock of 297 Mhz (UHD Color Off) - Intel driver is using those modes for 4K and they work fine:
4K 24/25/30Hz RGB 8-bit
4K 50/60Hz YCbCr 4:2:0 8-bit
When the EDID report the "high speed" pixel clock mode (594 Mhz) is available - Intel driver is using those modes (and they give no signal):
4K 24/25/30Hz RGB 12-bit
4K 50/60Hz RGB 8-bit
IMO the issue has something to do with Samsung having limited support for 4K RGB modes. It probably expects YCbCr 4:2:2 which Intel does not support.