I highly recommend checking out Justin’s blog for more of his posts, the most recent being in December 2020.

He’s a passionate cartographer, and has been posting about maps since 2010, 2017 being his rise to popularity not withstanding.

He’s actually not a "cartographer" and has no formal training in cartography.

(This misconception comes from a 2017 Verge piece on "Google Maps' Moat" that misstated that he was.)

Source/Disclosure: I'm a close friend.

What would be a better word to describe someone who is passionate about maps?

Perhaps I used the word “cartographer” incorrectly. I apologize, my native language is German so English is not always 100% forthcoming to me.

A "cartographer" is someone who makes maps for a living. So the word "cartographer" is a job title, similar to how "programmer" is a job title for someone who programs computers.

I don't think that there is an English word for someone who likes maps. The best thing to say is what you already said: that they are "passionate about maps".