Hi,
no, noting was cut of serial port features. However, you are on arm, not on x86, who knows. Serial port was tested and worked with various apps. But you know, android is completely different system and each if it’s versions may work differently. For example, internet connection requires special internet permissions. They should be granted automatically on installation. Did you try paste whole desktop dosbox config in expert settings? Maybe there is something what mdosbox disables by default like pcspeaker