If you are using Klipper in “USB to CAN bridge” mode then the micro-controller is not a “serial device” and will never show up in /dev/serial/. (When Klipper runs in “USB to CAN bridge” mode it instead behaves as a “gs_usb” can bus adapter.) When in this mode, it can therefore not be discovered as a serial device and is also therefore not impacted by a system issue involving the reporting of serial devices.
Cheers,
-Kevin