• Create the Digital Ocean Droplet
• Install quake3-server:

sudo apt-get update
sudo apt install quake3-server

• Copy your Quake 3 game files to /usr/share/games/quake3/baseq3

• Install both the Quake 3 package as well as the application game-data-packager to create a non-distributable Quake 3 data package: sudo apt install quake3 game-data-packager innoextract

• Package the data files: game-data-packager -i quake3 /usr/share/games/quake3/baseq3/pak0.pk3

• You can now start the server: quake3-server

• To use one of the sample configurations from the game, install unzip and unzip the necessary config files from pak0.pk3:

sudo apt install unzip
sudo unzip /usr/share/games/quake3/baseq3/pak0.pk3 ctf.config ffa.config teamplay.config tourney.config gamecycle.config
sudo mv /usr/share/games/quake3/baseq3/*.config /var/games/quake3-server/.q3a/baseq3/

• Edit the main configuration file: sudo vi /etc/quake3-server/server.cfg
• Uncomment the exec command to use one of the configuration files (e.g. exec ffa.config)
• Start the server using the main configuration file: quake3-server +exec /etc/quake3-server/server.cfg

You can now connect to the server from the game client by selecting "Specify" in the multiplayer server list and entering the Droplet's IP address.