Firefox has vanished from applications menu in Ubuntu 20.04

I use both Gnome and KDE Plasma on Ubuntu 20.04. I used the 'Edit Application' feature in Plasma to get Firefox to start using my dedicated graphics card. I also installed certain updates using Discover in Plasma (which I generally don't do). Here are these updates from the logs:

Upgrade: grub-common:amd64 (2.04-1ubuntu26.11, 2.04-1ubuntu26.12), ubuntu-advantage-tools:amd64 (20.3, 27.0.2~20.04.1), grub2-common:amd64 (2.04-1ubuntu26.11, 2.04-1ubuntu26.12), grub-pc:amd64 (2.04-1ubuntu26.11, 2.04-1ubuntu26.12), grub-pc-bin:amd64 (2.04-1ubuntu26.11, 2.04-1ubuntu26.12), grub-efi-amd64-bin:amd64 (2.04-1ubuntu44, 2.04-1ubuntu44.2), grub-efi-amd64-signed:amd64 (1.167+2.04-1ubuntu44, 1.167.2+2.04-1ubuntu44.2)

After this, I logged back into Gnome to see that Firefox has vanished from the Applications menu and the 'Installed' section in Software Centre. I can search for it in Software Centre and it says it's still installed. I can even access and launch it from /usr/share/applications. I can still run it on KDE Plasma. But on Gnome it just won't show up in the Applications menu despite uninstalling and reinstalling twice. I even undid what I had initially done on Plasma regarding the dedicated graphics card but that has not made any difference. Lastly, I tried to uninstall it on Gnome using Software Centre and then install it from Plasma using Discover, but it didn't help either. The odd thing is that I did the same setting change regarding the dedicated GPU for three other applications and they're all fine, but Firefox just won't appear in the Applications menu, so I'm not sure if the issue is being caused by editing the application or because of the updates I installed from Discover. How do I fix this?

UPDATE: Here is what I believe is the relevant content from the /usr/share/applications/firefox.desktop:

Exec=firefox %u
Terminal=false
X-MultipleArgs=false
Type=Application
Icon=firefox
Categories=GNOME;GTK;Network;WebBrowser;
MimeType=text/html;text/xml;application/xhtml+xml;application/xml;application/rss+xml;application/rdf+xml;image/gif;image/jpeg;image/png;x-scheme-handler/http;x-scheme-handler/https;x-scheme-handler/ftp;x-scheme-handler/chrome;video/webm;application/x-xpinstall;
StartupNotify=true
Actions=new-window;new-private-window;

I opened /usr/bin/firefox and these are its contents

#!/bin/sh

set -e

# Firefox launcher containing a Profile migration helper for
# temporary profiles used during alpha and beta phases.

# Authors:
#  Alexander Sack <[email protected]>
#  Fabien Tassin <[email protected]>
#  Steve Langasek <[email protected]>
#  Chris Coulson <[email protected]>
# License: GPLv2 or later

MOZ_LIBDIR=/usr/lib/firefox
MOZ_APP_LAUNCHER=`which $0`
MOZ_APP_NAME=firefox

export MOZ_APP_LAUNCHER

while [ ! -x $MOZ_LIBDIR/$MOZ_APP_NAME ] ; do
    if [ -L "$MOZ_APP_LAUNCHER" ] ; then
        MOZ_APP_LAUNCHER=`readlink -f $MOZ_APP_LAUNCHER`
        MOZ_LIBDIR=`dirname $MOZ_APP_LAUNCHER`
    else
        echo "Can't find $MOZ_LIBDIR/$MOZ_APP_NAME"
        exit 1
    fi
done

usage () {
    $MOZ_LIBDIR/$MOZ_APP_NAME -h | sed -e 's,/.*/,,'
    echo
    echo "      -g or --debug          Start within debugger"
    echo "      -d or --debugger       Specify debugger to start with (eg, gdb or valgrind)"
    echo "      -a or --debugger-args  Specify arguments for debugger"
}

moz_debug=0
moz_debugger_args=""
moz_debugger="gdb"

while [ $# -gt 0 ]; do
    case "$1" in
        -h | --help )
            usage
            exit 0
            ;;
        -g | --debug )
            moz_debug=1
            shift
            ;;
        -d | --debugger)
            moz_debugger=$2;
            if [ "${moz_debugger}" != "" ]; then
          shift 2
            else
              echo "-d requires an argument"
              exit 1
            fi
            ;;
        -a | --debugger-args )
            moz_debugger_args=$2;
            if [ "${moz_debugger_args}" != "" ] ; then
                shift 2
            else
                echo "-a requires an argument"
                exit 1
            fi
            ;;
        -- ) # Stop option processing
            shift
            break
            ;;
        * )
            break
            ;;
    esac
done

if [ $moz_debug -eq 1 ] ; then
    case $moz_debugger in
        memcheck)
            debugger="valgrind"
            ;;
        *)
            debugger=$moz_debugger
            ;;
    esac

    debugger=`which $debugger`
    if [ ! -x $debugger ] ; then
        echo "Invalid debugger"
        exit 1
    fi

    case `basename $moz_debugger` in
        gdb)
            exec $debugger $moz_debugger_args --args $MOZ_LIBDIR/$MOZ_APP_NAME "$@"
            ;;
        memcheck)
            echo "$MOZ_APP_NAME has not been compiled with valgrind support"
            exit 1
            ;;
        *)
            exec $debugger $moz_debugger_args $MOZ_LIBDIR/$MOZ_APP_NAME "$@"
            ;;
    esac
else
    exec $MOZ_LIBDIR/$MOZ_APP_NAME "$@"
fi

Here is a resolution for this issue. In my case, I just ran sudo dpkg -P firefox and then installed it from the Software Centre.