I'm in Debian 9.4 using X version 7.7. The game does not react at all when I'm pressing space. (It troublesome especially since the pause button become smaller since PoE1...)
xev gives the following:
KeyPress event, serial 48, synthetic NO, window 0x4200001,
root 0x10c, subw 0x0, time 14561642, (265,-77), root:(267,357),
state 0x4000, keycode 65 (keysym 0x20, space), same_screen YES,
XLookupString gives 1 bytes: (20) " "
XmbLookupString gives 1 bytes: (20) " "
XFilterEvent returns: False
KeyRelease event, serial 48, synthetic NO, window 0x4200001,
root 0x10c, subw 0x0, time 14561748, (265,-77), root:(267,357),
state 0x4000, keycode 65 (keysym 0x20, space), same_screen YES,
XLookupString gives 1 bytes: (20) " "
XFilterEvent returns: False