I had the same issue (Network and USB failure with trusty) - but I'm not sure which of the following fixed it:
This is the last few lines of my root console history:
1989 apt-get install linux-image-generic
1992 depmod -a
1993 update-initramfs -k all -c
1994 apt-get install linux-firmware
1995 apt-get update
1996 apt-get upgrade
1997 apt-get install linux-firmware
1998 apt-get install linux-firmware-nonfree
1999 update-initramfs -k all -c
2000 reboot
I'm guessing it'll be #1998 (firmware for network card) and #1989 (Installs the linux-image-extra-generic package; USB support) and #1999 (Rebuild the initramfs files; insert new modules/firmware into initrd)
Hope that helps.