Some days ago a stumbeled over this again.
Here my solution:
This is done in 2 steps: Setting the button background attribute to android:attr/selectableItemBackground creates you a button with feedback but no background.
android:background="?android:attr/selectableItemBackground"
The line to divide the borderless button from the rest of you layout is done by a view with the background android:attr/dividerVertical
android:background="?android:attr/dividerVertical"
For a better understanding here is a layout for a OK / Cancel borderless button combination at the bottom of your screen (like in the right picture above).
