Using an old desktop keyboard, thankfully the right Alt acts like AltGr, and Ctrl + Alt + Print Screen works.
An issue comes in when using Apple’s now-standard-across-all-its-devides compact keyboard layout (no dedicated print screen, no dedicated right alt). It results in a need to hit Control + Opt/Alt (for AltGr) + Fn + Shift + F11 (for Print Screen), and it fails miserably. It may be that Apple’s keyboard hardware can’t handle 5 simultaneous key presses, or maybe their driver can’t pass the intended key combos to Windows, but it’s a failure.
Let me see if the keyboard for the Surface Pro 3 (effectively a compact key layout, with no Print Screen) allows me to do anything… Fn+Spacebar replicates Print Screen OK, and Right Alt works (as does Ctrl + left Alt). So minus the hoops you must jump through, it works!
Well, I’ve learned something new: if you do a bunch of unwieldy key combinations, things may or may not work. I’d hate to see what happens with other keyboards; it seems all too easy to get into a sticky situation.
So it seems the right Alt keyboard is more respected than I thought, but it’s definitely an afterthought around these parts.