For some reason, downloading packages using
apt-get install was unusually slow on DigitalOcean this week, barely exceeding 4kbps. Since DigitalOcean droplets are configured to download packages from mirrors.digitalocean.com, all I had to do was to revert them to the default Ubuntu sources using these two commands:
sudo sed -i "s/mirrors.digitalocean/archive\.ubuntu/g" /etc/apt/sources.list sudo apt-get update
Downloads are now as fast as they should be.