Yet (not) Another Maps Pack (YnAMP) provides Earth maps in different sizes with true starting locations, as well as a few more features. Read more about them in the civfanatics forum post.
If you run Civ6 on a PC, see that forum post above for installation instructions. Do not use the "releases" tab here, as it's not updated.
Mac Steam Users use the following command:
cd ~/Library/Application Support/Sid Meier's Civilization VI/Mods/
Mac non-Steam users use the following command:
cd /Applications/Civ6.app/Contents/Assets/Base/Assets
Once inside this directory, clone this repo with the following git command:
git clone https://github.com/seelingcat/Civ6-YnAMP.git
If you do not have git, it can be installed here.
Enjoy!