You have installed packages via .deb files (for example Google Chrome or VSCode) and now you can’t find and uninstall them via your package manager GUI.
Worry not my friend, bellow is your beloved copy pastes.
Find full package name
$ dpkg -l | grep -i my-package
Replace my-package with partial name or description of your app.
Uninstall using apt
$ sudo apt remove my-app
Replace my-package with full name retrieved in previous step.