I've been running an instance of this on a DigitalOcean VM for a couple of years now. Keeping my instance external is nice so I can use it from home, work, and for friends and family, with all of my devices. Fantastic project, highly recommended.
I have a pihole at home (not a Rasperry Pi, gosh I wish they'd ditch the marrying of the two) but to access it I establish a VPN.
Recursive DNS resolvers on the open Internet start getting abused really fast for DNS amplification DDoS attacks (for anyone unaware reading this).