I have come to just accept the firmware will be read out in most microcontrollers unless they are specifically built to hold secrets. Maybe you can keep someone

I have come to just accept the firmware will be read out in most microcontrollers unless they are specifically built to hold secrets. Maybe you can keep someone from copying your code for a little while, but eventually it will happen and you should have some other value that protects your business. NRF, STM32, PSoC, ESP32, Xilinx. All of them have silicon or ROM errata that leak the firmware or the encryption around it.