Which Carriers Support eSIM in Germany?

Germany is an exciting destination for any traveller. From bustling Berlin to the quaint charms of Cologne, Germany offers something for everyone. Firstly, you'll need a mobile internet connection to get around. But what German mobile carrier should you use? Which data plan is the best value in Germany? What is an eSIM? How the heck do you set it up? I've got all the answers.