If you do this, please note that the ARM-side software needs to write a driver, because the CH340 chip is a USB device for ARM, and the ARM side needs a usb device driver.
CH340 chip is a USB to UART chip, note that it is not a level conversion chip like MAX232.
On the ARM side, no driver is required to drive MAX232.
It's important to note that this is not a simple replacement.
To replace, note that the CH340 chip device descriptor is the content of the USB specification. If you are not familiar with the USB specification and ARM-based USB device drivers, it is recommended not to replace.