Ubuntu images for these boards can be downloaded here.
Koheron Alpha250 is a Xilinx Zynq development board with 100 MHz RF front end.
It features two 14-bit ADC channels and two 16-bit DAC channels, both at 250 MSPS, clocked by an ultra-low jitter clock generator.
It includes 4 channel 24-bit ADC and 4 channel 16-bit DAC.
The board comes with open source reference designs.