Okay so the mount broke, it's too thin, in the area of the ring that attaches it to the Nimble under the drive cable. So I have added a spar to see if it helps and will try it again. Will post it if it works.
The filament monitor uses a relatively simple protocol to send the angle to the Duet every 50ms or so. I have not written up the documentation for the protocol yet, once I do then you could use a MCU to interface any encoder to the Duet using this protocol.