$ ls -al /etc/apt/sources.list.d/
drwxr-xr-x 2 root root 4096 Dec 15 21:13 .
drwxr-xr-x 6 root root 4096 Dec 15 21:41 ..
-rw-r--r-- 1 root root 103 Dec 15 21:13 additional-repositories.list
-rw-r--r-- 1 root root 170 Oct 20 13:56 freecad-maintainers-freecad-stable-bionic.list
-rw-r--r-- 1 root root 142 Dec 15 21:04 graphics-drivers-ppa-bionic.list
-rw-r--r-- 1 root root 514 Oct 4 21:21 official-package-repositories.list
-rw-r--r-- 1 root root 136 Dec 15 12:38 openscad-releases-bionic.list
-rw-r--r-- 1 root root 1509 Nov 19 18:14 teamviewer.list
-rw-r--r-- 1 root root 130 Dec 13 21:16 teejee2008-ppa-bionic.list
-rw-r--r-- 1 root root 193 Oct 5 20:28 vscode.list