Reading from serial port

[limpid vapor]

Hi,
I would be grateful for any help, suggestions, hints...
Configuration like this:

• HA (2025.10) as a VM in Proxmox 8;
• Prolific pl2303 converter connected to the USB port;
• USB passthrough as device ID;

Hardware recognized in HA - I see it in dmesg

dmesg -T |grep tty

[Wed Oct 8 23:00:19 2025] usb 2-1: pl2303 converter now attached to ttyUSB0

Cable/converter for 100% works fine - when I do

cat /dev/ttyUSB0

I see the correct messages on the terminal/console send by RS232 device

Configured serial in HA as:

• platform: serial
  baudrate: 2400
  serial_port: /dev/ttyUSB0

BUT the entity sensor.serial_sensor itself has state: unknown…

This configuration worked for more then years - what has changed:

• about month ago I had to replace RS232 end device but new one has the same RS232 parameters, configurations etc.
• updated HA from 2025.09.xx

[ancient idol]

i am suspecting it is setting related like permissions or baudrate. What does proxmox show when you shut down haos, is the data still received and readable?

[limpid vapor]

there is passthrough on Proxmox; I see all correct data on haos -> when I do cat /dev/ttyUSB0 on haos terminal all look correct; baudtare bits etc. are setted corretly... I've even checked in old backup files -> looks similar