Terasic ADA Daughter Card

For DAC channel A, you can remove T5 and add a zero ohm jumper for R60. You get a 50 ohms DC coupled single ended output.

An AD8132 or AD8138 could be used in a circuit according to the AD9248 datasheet. But there's neither a suitable place on the board nor a differential connector option to place it external to the board. So it must be glued to the board. It's possible to my opinion, but I don't want to suggest it generally.