Best way to do it .. use ClipGrab.
ClipGrab is distributed as an AppImage, so theoretically you could just download it somewhere, mark it executable, and run it .. but we're going to also add it to the main menu with an icon.
Open a terminal and run these commands in sequence...
Create a directory for the ClipGrab AppImage:
mkdir -p ~/.AppImages/ClipGrab
make it the current directory:
download the ClipGrab appimage into it:
wget -O ClipGrab-Latest.AppImage https://download.clipgrab.org/ClipGrab-3.8.5-x86_64.AppImage
make the ClipGrab-3.8.4-x86_64.AppImage executable:
chmod +x ~/.AppImages/ClipGrab/ClipGrab-Latest.AppImage
download an image to use as an icon:
wget http://icons.iconarchive.com/icons/papirus-team/papirus-apps/256/clipgrab-icon.png
create a launcher for it by running:
xed ~/.local/share/applications/clipgrab.desktop
and when a blank file opens, make it read:-
[Desktop Entry]
Type=Application
Name=ClipGrab
Comment=Download YouTube, Dailymotion, etc. Video Clips
Exec=/home/mark/.AppImages/ClipGrab/ClipGrab-Latest.AppImage
Icon=/home/mark/.AppImages/ClipGrab/clipgrab-icon.png
Terminal=false
StartupWMClass=ClipGrab
Categories=Network;
StartupNotify=false
(be sure to change the 2 instances of 'mark' to your username)SAVE the file.
You should now have a launcher at
Menu > Internet > ClipGrab