Yes it does work with Linux. I think there is a bit of a bug in the Linux kernel with respect to how it chooses UAC configs, it doesn’t always choose the best one!1 So on my MixPre it chooses config 1 (UAC-1), instead of config 2 (UAC-2).
Anyway, all I need to do with my MixPre 6 mk1 is tell the kernel to switch to config 2. You can do this using sysfs, or easier still with the usb_modeswitch command.
I have the following udev rule so that the command runs automatically when I connect the device.
# SoundDevices MixPre 6, switch to configuration 2
ACTION=="add", SUBSYSTEM=="usb", ATTRS{idVendor}=="0926", ATTRS{idProduct}=="0206", RUN+="/usr/bin/usb_modeswitch -v 0x0926 -p 0x0206 -u
You might find that the product id values are different for the MixPre 3.
Hope that helps.
1 one day I’ll finish writing a patch and try to get it submitted to the kernel…