CMUX on BG95-m3

I believe that the BG95-m3 module should support CMUX on UART1, but I can’t get it to work. I get “+CME ERROR: 3” when I try to enable it.

Should this work? what firmware was support added?
Can someone confirm if UART1 is the main serial port on the USB (/dev/ttyUSB2 for example).

Basically I’m trying to use CMUX to be able to send AT commands as well as having a PPP connection at the same time.

1.For CMUX issue , pls kindly open the below docs;

  1. Main URAT is different from the UART1

@Stephen.Li-Q so CMUX isn’t available over the USB uart, is that correct?