Install .Net Core

Something:

cd /tmp
curl https://packages.microsoft.com/keys/microsoft.asc | gpg --dearmor > microsoft.gpg
sudo mv microsoft.gpg /etc/apt/trusted.gpg.d/microsoft.gpg
 
sudo sh -c 'echo "deb [arch=amd64] https://packages.microsoft.com/repos/microsoft-ubuntu-$(lsb_release -cs)-prod $(lsb_release -cs) main" > /etc/apt/sources.list.d/dotnetdev.list'

Now Update, and install .NET SDK…

sudo apt update
 
PKG=$(sudo apt search dotnet-sdk | grep $(lsb_release -cs) | sed '$s/\//\n/g' | grep -v $(lsb_release -cs))
 
sudo apt install $PKG -y

If you want to serve web applications, see netcore