If you already have cables attached to the printer that solution is probably preferable to my workaround. There are no firmware changes needed.
For my solution I suggest that you try locate where the error is. The error is has probably nothing to do with braudrate setting, just that you are unable to connect. There are two general areas that might give you trouble, the setup on your RPi or your network.
There are a few simple things I could suggest you make sure is OK:
*The printer is powered on
*The printer and RPi is connected to your network
*You need to modify the last command before you send it. Make sure you understand the explanation in notes when you modify.
*You only need to install socat once. But the two others need to be runned every time you restart the RPi. (Once you get this working I would suggest you automate it)
*The terminals running the commands are active. Use two separate terminal windows sending the commands in correct order.
*The ports showing up in octoprint should be the same as the ones you recieve from the terminal.
*RPi and printer on same LAN.
*Try from same access point as RPi with a computer to use Qidi print and send print remotely