Why does the Super key show the desktop on Xubuntu 22.04?

Question

I have Xubuntu version 22.04.1. This has started to happen to me only recently, and is annoying as heck: pressing the Super (Windows) key minimizes all the windows to show the bare desktop. (Pressing it again restores the windows.) How do I stop the Super key by itself having an effect?

It is only the left-side Super key that has this effect. Pressing the right-side Super key has no effect. I have the Swedish+Finnish keyboard, in case that makes any difference.

In Settings => Window Manager => Keyboard, I have no action mapped to the Super key, and the action "Show desktop" is mapped to Ctrl+Escape. I tried remapping the action to another key, then deleting the mapping and remapping, but none of that helped.

In Settings => Keyboard => Application Shortcuts, I have no action mapped to the Super key, nor is there a definition for a command that would show the desktop.

I have never attempted to map an action to the Super key by itself, nor do I want to.

Question How do I disable the Super key? has answers relevant only to Ubuntu and the Unity desktop. (Unity was the reason I switched to Xubuntu.)

Edited on 2022-10-01 to add:

The output of localectl is:

 System Locale: LANG=en_US.UTF-8
                LANGUAGE=en
                LC_NUMERIC=en_GB.UTF-8
                LC_TIME=en_GB.UTF-8
                LC_COLLATE=en_GB.UTF-8
                LC_MONETARY=en_GB.UTF-8
                LC_PAPER=en_GB.UTF-8
                LC_NAME=en_GB.UTF-8
                LC_ADDRESS=en_GB.UTF-8
                LC_TELEPHONE=en_GB.UTF-8
                LC_MEASUREMENT=en_GB.UTF-8
                LC_IDENTIFICATION=en_GB.UTF-8
     VC Keymap: n/a
    X11 Layout: fi
     X11 Model: pc105

Edited on 2022-10-13 to add:

This is in reply to user Andra's suggestion to use screenkey. I installed it using apt, ran it, and started pressing keys. When I pressed either the the left-hand or the right-hand Super key (Super_L or Super_R) + m, screenkey displayed "Super+m". When I pressed and released the Super_R key, nothing happened, and screenkey displayed nothing. But: when I pressed and released the Super_L key, all the windows were minimized, as before, and screenkey displayed "Ctrl+Esc". (Pressing it again restores the windows.) As I mention above, the "Ctrl+Esc" shortcut is mapped to action "Show desktop" in Settings => Window Manager => Keyboard.

I then tried this: I remapped "Show desktop" to shortcut "Shift+Alt+F5". Now, when I pressed and released the Super_L key, screenkey again displayed "Ctrl+Esc", but there was no other effect. (Pressing Shift+Alt+F5 now did minimize the windows, and screenkey displayed "Alt+Shift+F5".)

I have no idea how the Super_L key came to be interpreted by the system as "Ctrl+Esc".

Edited on 2022-10-15 to add:

The output of setxkbmap -print -verbose 10 is:

Setting verbose level to 10
locale is C
Trying to load rules file ./rules/evdev...
Trying to load rules file /usr/share/X11/xkb/rules/evdev...
Success.
Applied rules from evdev:
rules:      evdev
model:      pc105
layout:     fi
Trying to build keymap using the following components:
keycodes:   evdev+aliases(qwerty)
types:      complete
compat:     complete
symbols:    pc+fi+inet(evdev)
geometry:   pc(pc105)
xkb_keymap {
    xkb_keycodes  { include "evdev+aliases(qwerty)" };
    xkb_types     { include "complete" };
    xkb_compat    { include "complete" };
    xkb_symbols   { include "pc+fi+inet(evdev)" };
    xkb_geometry  { include "pc(pc105)" };
};

Edited on 2022-10-16 to add:

The output of xmodmap -pke | grep Super is:

keycode 133 = Super_L NoSymbol Super_L
keycode 134 = Super_R NoSymbol Super_R
keycode 206 = NoSymbol Super_L NoSymbol Super_L

Edited on 2022-10-19 to add:

The output of gsettings list-recursively | grep -i escape is:

org.gnome.desktop.wm.keybindings cycle-panels ['<Control><Alt>Escape']
org.gnome.desktop.wm.keybindings cycle-panels-backward ['<Shift><Control><Alt>Escape']
org.gnome.desktop.wm.keybindings cycle-windows ['<Alt>Escape']
org.gnome.desktop.wm.keybindings cycle-windows-backward ['<Shift><Alt>Escape']
org.gnome.mutter.wayland.keybindings restore-shortcuts ['<Super>Escape']

Answer 1

The problem seems to be due to some sort of a bug with Xfce's keystroke mapping system. The solution was to clear, in Settings => Window Manager => Keyboard, my custom mapping of keystroke Ctrl+Esc to action "Show desktop".

I found out the following when configuring another laptop with Xubuntu 22.04 just installed. I was customizing the keystroke mappings (Settings => Window Manager => Keyboard). By default, the keystroke for "Show desktop" was "Super+D". Keystrokes Super_L+D and Super_R+D showed the desktop, as expected, and the key Super_L by itself showed the whisker menu (Xfce's equivalent to the Windows Start menu), which was unexpected.

I then changed the keystroke that maps to action "Show desktop" to Ctrl+Esc, as I had done on the laptop that first presented the problem. Immediately after this, keystroke Super+D did nothing anymore, as expected; keystroke Ctrl+Esc showed the desktop, as expected; and key Super_L by itself also showed the desktop, as certainly not expected, and which is the problem under discussion.

Clearing the mapping of keystroke Ctrl+Esc to action "Show desktop" resolved the problem. After this, Super_L did nothing anymore, whereas before I started manipulating the mappings, it showed the whisker menu, as mentioned. But I did not see an explicit mapping of Super_L to the whisker menu anywhere.