Is it possible to lock the iPad's screen by using a keyboard shortcut, when using a BT keyboard, or the SmartKeyboard?
Cmd+Shift+Eject as on the Mac does not work. Holding down the Cmd key also does not show any shortcut.
At this moment it is not possible with a keyboard shortcut. Some third party keyboard has dedicated buttons for locking and more...
I highly suggest you give this feedback to Apple!
I was able to figure out Control + Command + Q seems to work on the new iPad Pro keyboard to lock it.
Right now it may be possible if you have
Fn key on your keyboard.
L and the screen will be locked.
This works on my bluetooth keyboard(Logitech K375s), but I'm not sure whether it works on every keyboard.