https://fonts.google.com/?selection.family=Open+Sans
cd /usr/share/fonts
sudo mkdir googlefonts
cd googlefonts
sudo unzip -d . ~/Downloads/Open_Sans.zip
sudo chmod -R --reference=/usr/share/fonts/opentype /usr/share/fonts/googlefonts
sudo fc-cache -fv
fc-match OpenSans
http://www.binarytides.com/gorgeous-looking-fonts-ubuntu-linux
http://ubuntuhandbook.org/index.php/2016/05/manually-install-fonts-ubuntu-16-04
You can search the Debian Packages: https://www.debian.org/distrib/packages. For example, here is the search results for "fonts-inter": https://packages.debian.org/search?suite=default§ion=all&arch=any&searchon=names&keywords=fonts-inter. Usually, when you find a Debian package there will be an Ubuntu equivalent.
You can also search with the
apt
command itself.