When AltGr is pressed within Windows, this is translated to Ctrl+Alt. Much of guac is written to handle this, but the following recent addition renders those changes ineffective:
This is because when Ctrl+Alt is being pressed AND it's being pressed as a substitute for AltGr, we CAN expect a keypress event, and in fact must rely on the keypress, as e.keyIdentifier is unreliable here. Only keypress will have the correct key.
There is no way to distinguish between Ctrl+Alt used as AltGr and Ctrl+Alt used with a keyboard lacking AltGr other than the presence/absence of keypress. All keydown/keyup events are otherwise completely identical.