Hi, no. I'm using a Mac (both iMac and MacBook Pro).
Even though the RME was on, neither Volumio Uis would offer either the RME OR USB as an option. Next morning (having done nothing different - as far as I know), the RME came up as an option (NOT USB) on both. Strange!
All seems well now; I'm impressed with the machine; just wished there were more inputs and the manual and/or the hardware buttons etc were more intuitive, but I'd imagine, like most, I spend some time getting somewhere near the subjective optimum, and then leave the settings for ever and a day and then, if changes have to be made, spend the same amount of time, re-reading the manual!
I do have REW and their recommended microphone so I suppose I could try to measure my room acoustics and change the RME settings to suit, but at present, I'm happy with the improvement in SQ. and the REW manual too would need a comprehensive re-read.
I tried Mo0de player (I have a version from several years ago) but downloaded the latest version and could not get that to work (it too has a dedicated USB-out option). I may try pico player - just out of interest, but I must admit, at present Volumio does most of what I want, and, contrary to some views, appears stable and updates without needing to re-toast a micro-SD card.
Thanks for your interest,
Richard