Do I absolutely have to have a bootloader during development for a custom STM32MP13 board?

[cbcooper]

I've got a custom board built around an STM32MP135AAE3.  It's designed to have an eMMC instead of an SD card, the problem is that the board was not laid out correctly and the JTAG isn't connected.

I'm having trouble writing to the eMMC (that's another topic) but I'm trying to make some progress while waiting for a board spin.  The board is in serial boot mode so I'm able to upload bootloaders, am I allowed to upload any arbitrary program and call it a bootloader?  I'm thinking I could start testing board features by uploading small programs to test the board if that's allowed with a "bootloader".

[PatrickF]

I'm not SW expert, but using other pins for UART (I guess you have some free pins on your board were you can plug RX/TX) is matter of updating this file https://github.com/STMicroelectronics/STM32DDRFW-UTIL/blob/main/DDR_Tool/STM32MP135C-DK/Inc/stm32mp_util_conf.h in the STM32MP135C-DK CubeIDE project (of a new cloned one) as described in https://github.com/STMicroelectronics/STM32DDRFW-UTIL?tab=readme-ov-file#1233-customization 

I assume that for your specific project constrains, choosing an MPU (STM32MP family) rather than MCU (other STM32 families) has been done with carefully assuming that learning curve for those is much steep and deserve solid embedded FW team background.
Alternatively, there is plenty of ready made HW as well as HW and SW partners available (https://www.st.com/content/st_com/en/partner/partner-program.html).

I cannot help much more on my side but maybe some peers in the ST Community have worked on a similar project and can share their experience here.

Do not hesitate to create new posts on specific points you want helps. It is very hard to manage wide questions on a single post.

Regards.