Shortcut Recording shows ោ for Right Alt key(Qt::GroupSwitchModifier or ISO_Level3_Shift)

Tried latest Qt Creator 4.12.4 on a Ubuntu 20.04, GNOME 3.36.3, Tools->Options->Environment->Keyboard(Tab), select one item and click "Record", looks like get similar things in description, ោ plus extra thing, for example, RALT+a, normally got å in examples/widgets/mainwindows/application and Terminal application, got something like " ោ?, Å" at previous Shortcut recording place.

$ setxkbmap -v
Trying to build keymap using the following components:
keycodes:   evdev+aliases(qwerty)
types:      complete
compat:     complete
symbols:    pc+us(mac)+us:2+inet(evdev)
geometry:   pc(pc105)

In /usr/share/X11/xkb/symbols/us, it has include "level3(ralt_switch)" in xkb_symbols "mac" section.