The USB port on my MOX A also stopped working with TOS 6. I have the MOX Classic and removed pre-installed the SDIO wifi-card. Because of the known SDIO bug, Turris kept the people with MOX with SDIO wifi-card with HBS on TOS 5.4.5. This probably means most people with MOX Classic didn’t get the big upgrade yet. Did you remove your SDIO wifi-card too, or did you buy a MOX without it (e.g. MOX Shield)?
The USB port on the MOX A module does not work. I was using the MOX as a NAS too. The drive I use has external power source. I tried installing kmod-usb3, but didn’t help.
Logs from 5.4.5: ZeroBin
root@moxclassic:~# lsusb -t
/: Bus 03.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 5000M
|__ Port 1: Dev 2, If 0, Class=Mass Storage, Driver=usb-storage, 5000M
/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 480M
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=orion-ehci/1p, 480M
Logs from 6.0.0: ZeroBin
root@moxclassic:~# lsusb -t
/: Bus 03.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 5000M
/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 480M
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=orion-ehci/1p, 480M