I have an STM32G031K8 Nucleo development board and was thinking about interfacing it's GPIO with an old BCD-to-Seven-Segment Decoder integrated circuit (SN74LS47N). This is a 5V part... and while I know that the GPIO pins are "5V tolerant", I don't know whether it is safe for these parts to be connected under power up/power down sequences when the microcontroller may be off while the IC is powered.
The IC input pins has this input circuit that has an internal pullup to 5V with some additional Schottky diodes to protect the IC. If the IC is powered and the microcontroller is not, will the microcontroller be damaged? The STM32G031K8 datasheet says the GPIO pins can only withstand, at worst, a voltage of Vdd + 4.0... but then again there is very little current available to drive into the pin.