I'm trying to add a serial console port functionality to the Up Squared 7100 running Ubuntu 24.04. I have been following along with this guide:
https://github.com/up-board/up-community/wiki/Serial-Console#Ubuntu

I have edited the serial.cfg to be

GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX console=tty0 console=ttyS4,115200n8"
GRUB_TERMINAL_INPUT="console serial"
GRUB_TERMINAL_OUTPUT="gfxterm serial"
GRUB_SERIAL_COMMAND="serial --unit=0 --speed=115200"

and run update-grub

Whenever I reboot the system it gets stuck and wont fully boot.

I'm not sure which tty device I should be using as I don't believe the Up Squared 7100 is classified as an UP Xtreme or an "upboard" based on the table here: https://github.com/up-board/up-community/wiki . I've tried with this config line too
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX console=tty0 console=ttyS5,115200n8"
"Note: in the below configurations, use ttyS5 (instead of ttyS4) if using UP Xtreme, use ttyS0 (instead of ttyS4) if using upboard"

I have been able to send data using ttyS5 from the 7100 and read out that data from a logic analyzer. But when using a FTDI USB Serial Device converter connected to CN3, I'm unable to receive correct data through the USB console port.
on the machine that's connected via usb to the 7100 sudo dmesg gives back this after sending data from the 7100

[ 1484.308411] usb 1-5.1.1.1.1: FTDI USB Serial Device converter now attached to ttyUSB0
[ 1912.473252] ftdi_sio ttyUSB0: usb_serial_generic_read_bulk_callback - urb stopped: -32
[ 1912.473501] ftdi_sio ttyUSB0: usb_serial_generic_read_bulk_callback - urb stopped: -32
[ 1917.180331] ftdi_sio ttyUSB0: failed to set flow control: -32
[ 1917.180506] ftdi_sio ttyUSB0: failed to get modem status: -32
[ 1917.380951] ftdi_sio ttyUSB0: ftdi_set_termios urb failed to set baudrate
[ 1917.381253] ftdi_sio ttyUSB0: failed to set flow control: -32
[ 1917.381553] ftdi_sio ttyUSB0: failed to get modem status: -32
[ 1917.381717] ftdi_sio ttyUSB0: error from flowcontrol urb

Anyone have an idea on how to get this working?