altwin:left_meta_win - super and meta on same key - how to fix

Hi,

I'm using GNU Emacs 30.1 (build 2, x86_64-pc-linux-gnu, X toolkit,
cairo version 1.18.4, Xaw3d scroll bars) of 2025-07-18, from Debian
package emacs-lucid version 1:30.1+1-6 on xorg version
1:7.7+24+deb13u1 with xkb-data version 2.42-1.

My keyboard is a Microsoft branded one, with menu, left and right
"Microsoft Windows logo" keys and emoji key, along with a top bar of
"multimedia" keys that are physically distinct from the F1-F12 keys.

My /etc/default/keyboard contains

XKBMODEL="microsoft4000"
XKBLAYOUT="us"
XKBVARIANT="euro"
XKBOPTIONS="altwin:left_meta_win,compose:menu"
BACKSPACE="guess"

I've been using altwin:left_meta_win since "forever", certainly since
I've had keyboard with "Microsoft Windows logo" keys, which might be
as long as I've been using GNU/Linux and X11, a few decades ago. Its
effect is to put the meta key on the left "Microsoft Windows logo"
key, so that I have separate Meta key (useful in Emacs) and Alt key
(that I use mainly for window manager bindings).

But now Emacs has started to treat the left Microsoft Windows logo key
as meta _and_ super at the same time, so that any binding in emacs
that uses Meta is unusable, because emacs will say I pressed M-s-FOO
when I pressed left Microsoft Windows logo key + FOO, which used to be
just M-FOO. For example, left Microsoft Windows logo key + d, instead
of being understood as M-d (bound to kill-word) is being understood as
M-s-d and emacs says "M-s-d is undefined".

I don't know if the change comes from an upgrade of emacs or of
xkb/xorg, as I rarely close my emacs (daemon) or my X11 session (I
rebooted for the latest high impact Linux security holes, my uptime
before that was > 300 days).

I would really really appreciate any hint on how to fix this.

Thanks!

-- 
Lionel