I havn't messed with CANopen so at the moment I couldn't give you an answer. If there is a library that uses it and it's working on teensy (most likely with old flexcan library), I may try to port it over. IFCT allowed alot of old flexcan library emulation for Teensy 3.2-3.6, but not adapted to T4 yet. Do you have an official link to teensy version of CANopen I could look at?