mcu:'mcu' unable to connect

[Alexandrinn]

please add in the comment to the printer configuration that when creating the firmware in Klipper Firmware Configuration you need to activate [*] Disable SWD at startup option

For anyone else having this issue

--- I had to "enable extra low level configuration options"
--- Save the config
--- Exit the config

And run the make menuconfig command again to open it back up. Once you do this you should see the option on the main screen and actually be able to select it

(Before I was just searching for the command and it was red and unable to be selected”

[bootuz-dinamon]

Wrong USART.
You need USART1 PA10/PA9 for Ender 3 V3 SE type-c connect.

[Alexandrinn]

Wrong USART. You need USART1 PA10/PA9 for Ender 3 V3 SE type-c connect.

The images are not mine, I took them only for a visual example...

[alex-elivate]

I didn't have to disable SWD, but I did need to flash my firmware twice. The first one looked and acted like it took, but wouldn't connect. I did a make clean and with the same config did another make, re-flashed it, and it worked right away. I'm wondering if this may cause some false starts for some people.
Anyway, success here. I just had to adjust my stepper_x positions to -10 so it wouldn't print off the bed to the left. Great work on this. I'm thrilled.