I didn't test running the Scarlett 18i20 software in wine or using a
VM. I suspect the culprit is, that any kind of virtual
machine/emulation still rely on the host's drivers/kernel modules.
Did you try to add the 18i20 ID to the Linux thingy (I've forgotten it's
name) available for the Scarlett series?
I don't care for two reasons, until now I only used the 18i20 2nd Gen
for my iPad and even if should use it for Linux, I simply would need a
class compliant interface, the same way it's used with the iPad.
I'm using Linux for mixing purpose with a RME HDSPe AIO. The next
interface I much likely will buy is a RME Babyface, for usage in class
compliant mode, too. The loss of HDSPmixer is much harder, than missing
the Focusrite mixer, but actually class compliant usage without
proprietary/vendor specific software is the most painless way to go.
--
$ pacman -Q linux{,-rt{,-cornflower,-pussytoes}}|awk '{print $2}'
4.14.4-1
4.13.13_rt5-1
4.11.12_rt16-1
4.14.3_rt5-1