Hi, you can use a lot of different JTAG or SWD programmers commercially available, for example the ST-Link. Alternatively, you can use the embedded bootloader to program the MCU using USART, I2C, SPI and in some cases other interfaces.
What MCU?
BR,
J
To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.