Okay, I actually figured it out for myself. I needed to install the "cups-32bit" package because my printer is like 15yr old. Aside from that, my config copying strategy was sound. I will attach a tarball of the config files with a list of where they belong. I would love to share the files with you but some are copyright Brother 2006. The summary is to copy the PPD from the working system, copy the filter file, chmod +x the filter file, install "cups-32bit" and "psutils", and copy the "Brother" director that the working filter file refers to.

Howdy, folks. I'm new to Solus and experienced with Linux, and am loving Solus so far. I have gotten the Brother MFC-665CW working on Solus over the network by copying config files I had on an opensuse machine - felt pretty clever after reading through all the scripts and understanding where the files had to go. However, while this did work on one Solus machine, I then tried it on another to no avail, though everything else I can find seems the same. I would be thrilled to get some help figuring this out, and I would also be thrilled if the drivers available at Brother's site - https://support.brother.com/g/b/downloadtop.aspx?c=us&lang=en&prod=mfc665cw_us_as - could be ported to Solus.