Going into F11 fullscreen and tapping Alt-Tab or Super (Window) key to return to desktop caused Minecraft to glitch, flashed semi-transparently. It looked like it's showing alternate frame page-flipping on desktop transparent layer or something like that. Minecraft blocked access to the desktop. Alt-Tab to Minecraft widget did not return focus to minecraft. Could not therefore exit fullscreen and it remained in the glitchy state. I was forced to reset the computer manually.