The RME Fireface UCX is a professional interface with 18 i/o channel (8 analog, 2 mic preamps), MIDI, S/PDIF and ADAT. It has both Firewire (400) and USB 2.0 (class compliant).
Its not officially supported under Linux but works with Ubuntu-Studio.
In CC (Class Compliant) mode the RME Fireface UCX works out of the box without having to use a patched kernel or flashing some firmware (tested with USB connection in Ubuntu 18.04 LTS).
ALSA will see only one channel, but after installing QJackCtl from Ubuntu-Studio installer everything works with Jackaudio (QJackCTL).
Listed audio channels in Jack correspond to:
CH 1-8 ⇒ Analog 6.3mm Jack Out
CH 9 - 10 ⇒ Spdif
CH 11 -18 ⇒ Adat (Tosink)
You might run some pre-start and post-start scripts from QJackCtl to get rid of some pulseaudio standard routings to the first 2 channels.
see here. Get working scripts here.
We figured out that custom routings are only loaded when QJackCtl is started from GUI rater than activated from command line only.