Is it possible, during the U-Boot stage in L4T 35.1, to send information only to the debug serial port without sending it to other serial ports?

[KevinFFF]

Please run the following command to check if it could help for your case.

$ sudo systemctl stop nvgetty.service
$ sudo systemctl disable nvgetty.service

and share the result of the following commnd:

$ cat /proc/cmdline