I've been using the cups/docker workaround (thanks again!) but it got stuck in a state where I can see in the CUPS UI that it accepted print jobs but was stuck saying "Waiting for printer to become available.". The job numbers were in the 40s so it was working for a while before this happened.
Nothing I tried helped - canceling and reprinting the jobs, powercycling the printer, stop and starting the container, etc... there are some "solutions" on the net (i.e.
https://www.linuxquestions.org/question ... 175652261/) about messing with udev that I'm not sure are applicable in a container environment - we're definitely running up against the amount I understand about both docker and udev/dbus at this point. So, eventually I went into container station and deleted the container and images, then ran the "docker run" command again, then set up the printer again, then it worked.
But, after the NAS rebooted I couldn't get to the cups UI anymore, and via `netstat -na` outside the container I could see it wasn't listening. So, I went into container station and added port forwarding from 631->631 TCP and the UI worked again... but the printer was again stuck in "Waiting for printer to become available" state. So, again, I deleted the container and images and set it up from scratch and it worked.
So, my current theory is that something is not persisting properly across reboots. Not sure why the port forwarding was OK the first time but not the second time, or what exactly is making the printer stop working. I did check all the settings this time in container station and see the port 631 forwarding as well as /var/run/dbus (read/write) under Shared Folders (both of those are in "Advanced Settings"). So, next time I reboot I'll see if it works and if those things persist. But, any thoughts / advice welcome - is this working ok for others?