Normally it should be detected. Look to see if something is different from
the ls /dev/usb and /dev/usb when plugged in and when it's not plugged in.
Or simply try to directly install the drivers I've send you.
Other think that you can do is to try Ubuntu in a USB Stick (the same as your
version of Trisquel), and see if it works out of the box. If it's the case
then it's is a missing package from Trisquel, otherwise it's another problem.
PS: Also check if you have the hpijs package installed, I don't know if this
is the one used for your printer (even if I'm pretty sure it isn't) but since
it is the one necessary for my HP PSC 1200 Series.. anything could be
possible.
