Describe the bug
The speed for the I2C5 peripheral is always ~16.8kHz and not the expected 100kHz on the Nucleo-H723ZG board and possibly other H7 variants. It does not change for different values of Wire.setClock(values). The other I2C peripherals behave as expected.

To Reproduce
Minimal reproducible example code:

#include <Wire.h>

void setup() {
  // set Wire to Pins associated with I2C5:
  Wire.setSDA(PC_10);
  Wire.setSCL(PC_11);
  Wire.begin();
  Wire.setClock(100000);

  // send any I2C message
  Wire.beginTransmission(0x24);
  Wire.write(0);
  Wire.endTransmission();
}

void loop() {
}

Results in ~16.8kHz on SCL Pin PC11 (see image)

Expected behavior
Expect 100kHz clock speed.

Screenshots
Measurement of Pin PC 10 (red) and PC11 (brown):

Clock speed around 16.8kHz.

Desktop (please complete the following information):

• OS: Windows 11
• Arduino IDE version: 2.3.3
• STM32 core version: 2.81
• Tools menu settings: default
• Upload method: Mass storage

Board (please complete the following information):

• Name: Nucleo-H723ZG
• Hardware Revision: Rev E01
• Extra hardware: no

Additional context
I think that the issue is in the i2c_getClkFreq(I2C_TypeDef *i2c) function. I single stepped the code and this snipped always returns 0 for the I2C5 peripheral clock frequency clkSrcFreq: