Whether or not your MAC Address will change will be determined by your WiFi settings:
Settings > WiFi > [Your WiFI Network Name / SSID] - tap the blue "i" icon - Private WiFi Address > select OFF, Fixed or Rotating as required
- OFF - Your iPhone will use its unique burned-in MAC Address that was assigned during manufacture.
- Fixed - Your iPhone will use a randomly selected MAC Address; this MAC Address will always be used for this WiFi connection.
- Rotating - Your iPhone will use a randomly selected MAC Address; this MAC Address will change periodically, or when reconnecting to this WiFi network connection.
Be aware that the Private Address feature is largely unnecessary for your home WiFi network; if enabled, Private Addressing can cause issues if specific MAC addresses are expected by your WiFi Router. You may need to disable this feature - and can be enabled or disabled for each individual network.
Use private Wi-Fi addresses in iOS 14, iPadOS 14, and watchOS 7 - Apple Support