Icon is duplicated on KDE Plasma Task Manager

Happens on Kubuntu 22.04.1 LTS.
Does not happen with GNOME's dock on Pop OS.
Install the app from either the AppImage or the Flatpak.
Pin it to Task Manager using the Application Launcher.
Press the newly created icon.

The program launches as a separate icon, unable to be pinned itself.

After some messing around with the AppImage and making a custom desktop file, I managed to find a solution. Since I'm still very new to all of this I don't know if this solution is acceptable or some kind of workaround to a larger issue.

This is the desktop file I have now:

[Desktop Entry]
Name=WhatsApp
Exec=/usr/local/bin/whatsapp %U
Type=Application
StartupWMClass=whatsapp-desktop-linux
Icon=io.github.mimbrero.WhatsAppDesktop
Comment=An unofficial WhatsApp client for Linux, built with Electron.
Terminal=false
Categories=Network;Chat;

Took some things from the Flatpak and others from Caprine as a working reference.

The particular line that seems to have fixed my issue and combined the icons is this one:

StartupWMClass=whatsapp-desktop-linux

mimbrero / whatsapp-desktop-linux

Icon is duplicated on KDE Plasma Task Manager #34

Does not happen with GNOME's dock on Pop OS.