Minecraft 18w20c, Minecraft 18w22c, Minecraft 1.13-pre2
Any keyboard that have the F3 key bound to any computer's setting (such as brightness, volume...)
All PCs that have the F3 key linked to any computer's setting (like brightness or volume) cannot use the F3 debug screen alone (without using shift+F3 or alt+F3). The game (or the computer) always prioritizes that setting over the Minecraft's debug screen unless using shift+F3 or alt+F3.
This makes F3 key combinations completely unusable.
The pie memory chart may hide some F3 information (block states) and causes unnecessary fps drops.
This can be solved by making the debug key editable in controls settings like every other key.