i tested the AES output from Ambre to my DAC too and the sound was nearly as good as with I2S.
With I2S connection it is minimal better at room informations, but both connections are at a very high quality level and do beat my old streamer in sound.
The Ambre uses a Pi with femto clocks and galvanic isolation on the outputs and has a very good power supply section.
So i think even without using the I2S it is a good alternative to other roon endpoints with the need of a external power supply.