It occurred to me that Zbigniew Baniewski wrote in gmane.os.netbsd.general:
> Is the /dev/lpa0 in some way "tied" only to "parallel port-driven" printers?

Yes, very, as the manpage explains:

(from man 4 lpt)

FILES
     /dev/lpt0    first interrupt-driven parallel port device
     /dev/lpa0    first polled parallel port device

So, yes, lpa is very tied to the parrallel port device, and you really
shouldn't use it to begin with, if you can avoid doing so.  You really don't
want a polled driver if you can afford an interrupt driven one.