Mine is the same black screen with windows and remixos options, however I am unable to change anything, and at the bottom of the screen it says "press ? or ? to change selection" along with other options like c or e for command line or edit, but I can't select anything even with the hardware keyboard on my Venue 11 Pro 7140, or a usb keyboard. Selecting remixos from the blue windows boot menu loads up.
You can get to the windows advanced boot options to select remixos by loading windows 10, holding down the shift key while pressing "restart". From there, I believe you press advanced boot options, then select remixos.
To the devs or other users, what exactly IS the black boot menu... is it grub? Where is the menu config stored? Is there any way to change the menu and activation keys to perhaps use the volume up/down and windows button so I can use the tablet keys without the keyboard attached?