Are there printers that NetPrint does not support?

Because HP has moved the print-rendering engine out of the printer and into the driver on the host system, the HP LaserJet 3500 and others (1012 and 1500) can only accept plain ASCII text as input from systems that do not have a 3500 driver. The LaserJet 3500 expects to receive a rasterized image of a print job from the PC driver and anything other than ASCII or a raster image download is rejected. The HP LaserJet 1500 is made in the same way.

Other color LaserJet models support full onboard PCL processing and will work with the HP3000. The 3700 might be a substitute for the 3500.

As to the Canon MF8170c the Canon Support Team had the following to say:

“Unfortunately, the MF8170c will not support the configuration you have inquired about. It uses proprietary Windows drivers only, which will not support PCL format.”  -Canon Support