Since the 51.1.6.1/54.1.2.1 update, and continuing with the latest 51.1.6.2/54.1.2.2 update, Fire TV devices now enable HDCP immediately at boot up.
It used to be that connecting the Fire TV to a non-HDCP compliant display resulted in normal operation until you tried playing copy-protected video. Quick Fix Amazon Fire Stick Black Screen
Which would then cause the screen to go blank.
Starting with updates 51.1.6.1/54.1.2.1, if connected to a non-HDCP display, during bootup of the Fire TV you will see the white Amazon logo followed by the colorful Fire TV logo as expected, then it immediately goes to a blank black screen.