Most audio interfaces of any substance don't work under Linux. If you're looking for simple 2 channel interfaces or something like that, there's a plethora available that work nearly out of the box. If you're looking for serious multichannel, there's compromises left and right. It wasn't until a couple years ago that my Fireface 800 was made to work with ffado and, coincidentally, the FF800 has been discontinued since then.
The audio professional would either need to have a lot of hardware processing for the quality to remain up. Having worked in the Mac world where you have access to things like Universal Audio plugins as well as other 3rd party plugs, it's a lot cheaper to be on OS X or Windows. Sure, the UAD 1176 doesn't sound exactly like the hardware 1176 (I'd say 80% of the way there), but it also costs a fraction of what a hardware 1176 costs and can be used across all the tracks you have enough DSP for at once.
Of (off-topic) potential interest to the Slashdot crowd, the RADAR still runs BeOS all these years later.