Hi,
I have working with STM32 since 2011. to read internal voltage of STM32 we can use ADC. one of internal STM32 ADC pin has been connected into internal voltage, so we can utilize it. I think internal temperature too, but let's explore it. I'm familiar with most of STM32 perpherals so doing this task isn't a big deal and I think it can be done in couple of hours.
Most of my projects were used STM32. I'm very familiar with this MCU, from STM32F0 to STM32F7. I will use STM32Cube IDE for the project.
just message me and let's get started.
Best Regards,
Rijal