firefox unable to show up in brisk-menu when installing firefox.desktop to system directory

[wmzart]

After installing the non-snap version of firefox using apt install, I added an icon and a firefox.desktop file, validated it and installed it, but firefox did not show up in brisk-menu. The desktop file is present in /usr/share/applications/

These are the commands I used to install (Please find files below):

sudo xdg-icon-resource install --novendor --size 128 default128.png firefox
sudo gtk-update-icon-cache
desktop-file-validate firefox.desktop
sudo xdg-desktop-menu install --mode system --novendor firefox.desktop

When navigating with caja to /usr/share/applications/, firefox starts as expected.

A workaround to make it appear is to name the file not firefox.desktop but something else. For example firefox-foo.desktop

With that filename the entry shows up in brisk-menu as expected.

Also, when installing firefox.desktop without sudo it installs to ~/.local/share/applications/ and does show up in brisk-menu.

Another workaround to make firefox appear in brisk menu is to invoke mate menu and enable a predefined firefox entry from there. Once enabled a firefox.desktop appears in ~/.local/share/applications/
For this workaround, commands from above or not required at all.

Does someone have any idea, why firefox.desktop is reserved when installing onto the system?

inxi -Sxxxz
System:
  Kernel: 6.8.0-50-generic arch: x86_64 bits: 64 compiler: gcc v: 13.3.0
    clocksource: tsc
  Desktop: MATE v: 1.26.2 wm: marco v: 1.26.2 with: mate-panel,plank
    tools: mate-screensaver vt: 7 dm: LightDM v: 1.30.0 Distro: MATE 24.04.1
    LTS (Noble Numbat) base: Ubuntu

firefox_launcher.zip