Hi, while trying to create a pyautogui script i found the following issue.
asweigart/pyautogui#186

I'm not sure if the issue comes from xlib or the underlying os configuration.
i upgraded from Linuxmint 17.1 to 19.3 over the past years. So maybe a config file is wrong as the other guy also has issues with linuxmint.

xev output

KeyRelease event, serial 38, synthetic NO, window 0xb800001,
root 0x1d3, subw 0x0, time 427025833, (-402,200), root:(459,655),
state 0x90, keycode 108 (keysym 0xfe03, ISO_Level3_Shift), same_screen YES,
XKeysymToKeycode returns keycode: 92
XLookupString gives 0 bytes:
XFilterEvent returns: False

showkey output

key code 100 pressed
key code 100 released

xmodmap -pke

keycode 92 = ISO_Level3_Shift NoSymbol ISO_Level3_Shift
keycode 108 = ISO_Level3_Shift NoSymbol ISO_Level3_Shift