Set Baud rate beyond 230400 on Linux

Hi all
I am working on a Terminal tool using SerialConnect. It works fine on Mac and Windows, even on Linux Ubuntu 18.04 (tested only at 9600 Baud). The highest option you can choose in SerialConnection is 230400. In my case I have a device connected that supports 2000000. This works fine too on Windows and Mac, not on Linux. I even can set that value also on Linux by SerialConnection and no error message/Exception pops up but that Baut rate doesn’t work (nothing or screwed up text returned from serial device). After some research I found an option on Linux to set the baudrate in terminal:

stty -F /dev/ttyUSB1 2000000 (no need for sudo, I/the app user is in the callout group with required permission to set it)

After this it worked like a charm in my App! Based on that I am thinking of doing a shell call whenever the user changes the Baud rate (possible in the Settings. I’m just wondering why SerialConnection working beyond 230400 fine on Windows and Mac but differs on Linux. Anyone has an idea or do I have to consider something else on Linux side to make it working like on Windows/Mac?