I have a dual boot system too, Ubuntu Mate for Pocket 2 and Win 10. To run Windows, which I need sometimes, I have to hit FN+F12 to get a BIOS boot option menu - otherwise it starts automatically Ubuntu. If I don't do that I have no grub menu like normally on multi boot machines where you can choose the os to boot - just a black screen for maybe 15 seconds and then Ubuntu Mate ist starting. Does anybody else see this behavior? Both OS are working cool, it's just the lack of a grub menu.