“serial = /dev/serial/by-id/usb-1a86_USB_Serial-if00-port0”
Looks good.
“mcu ‘mcu’: Timeout on connect”
See https://klipper.discourse.group/t/mcu-serial-connection-closed-timeout-on-connect-wait-for-identify-response how to fix that.
Do you have a fresh klippy.log? If yes, please post it here.