The cheaper Brother printers don’t have a PostScript engine, so you need a “driver” (really a CUPS filter) to rasterize the image and prepend the appropriate PCL commands. In the official Linux driver package, at least for my printer, this comes in the form of a rather complicated shell script that hooks together some binary blobs, and if you don’t have all the right 32-bit support libraries it just mysteriously fails to produce any output while CUPS reports that the print job completed successfully.

Fortunately someone has made an open-source equivalent which is much less complicated and seems to work just fine.