For what it’s worth, my experience is the same as CJ’s. I’ve installed Raspian Lite 4.4.x, and am running Roonbridge, outputting via HDMI into a Linn DSM. Sampling rates up to 192 kHz are working fine, but 24 bit material is being truncated to 16 bit.
By the way, the sound quality of this solution is good (notwithstanding any truncation) – much better than I expected, actually. I am not sure if the DSM is implementing audio rate control (via CEC) for its HDMI input, but for whatever reason this configuration seems to sound better than feeding the SPDIF output from a Squeezebox Touch into the DSM.