Summery:
After 3.36 upgrade, the right Mod4 key has become an additional Mod3 key on the keyboard

Affected version:
I'm using 5.6.6-arch1-1 with gnome shell 3.36.1, the issue appears in Xorg and Wayland. It is only present in GNOME, selecting a different desktop environment (UKUI) it is not present.

Bug summary:
After the upgrade to 3.36 on my German neo 2 keyboard layout (https://www.neo-layout.org/) the right Mod4 key has become an additional Mod3 key. Otherwise the keyboard layout is the same, so I have a Mod 3 and Mod 4 key on my left hand side, but two M3 and no M4 keys on my right.

Steps to reproduce:
- in gnome settings select the German neo 2 keyboard layout
- press the right Mod4 key (on qwertz keyboards AltGr) and for example the qwertz key Y.

What happened:
A hashtag appears "#", expected for a pressing Mod3 and the Y key

What did you expect to happen:
The equivalent to pressing the <ESC> key

First I thought it is an upstream gnome bug, so I opened an issue:
https://gitlab.gnome.org/GNOME/gnome-shell/issues/2425

But today I checked with Ubuntu 20.04 and gnome-shell 3.36.1: the keyboard layout is unchanged and works as expected. So I think the problem is with the arch package, it was already present with gnome-shell 3.36.0, see the gnome issue.