'mcu': Unable to open serial port

[Sineos]

@Sineos

Some distributions install services that might interfere with Klipper. Most noteworthy are

• ModemManager
• BRLTTY

# List all brltty services (replace with "modemmanger" to check this)
sudo systemctl list-units | grep brltty
# For each item in the result list of the above command run
sudo systemctl mask brltty.path
sudo systemctl stop brltty.path
# "brltty.path" is only an example. Replace it with the first command's output

Just follow this with modemmanger instead of brltty. It is a system service and has nothing to do with what you have connected.