My most favorite dedication (sorry for ruining the special moment for you!) is from a book by Terry Eagleton, called "On Evil". There's an almost blank page which simply reads:
I've revisited SS2 several times (couldn't play it due to REALLY ENORMOUS stress level) and I was able to finish it some 10 years later. What an atmosphere. What a story. What an absolute gem...
It's super easy and works every time. You might want to change NIX_CHANNEL=nixos-19.09 to NIX_CHANNEL=nixos-20.03 since 19.09 is the previous stable version. I use nixos-infect along with Morph so I don't care about the custom images that much - a fresh/bare NixOS is all I need to build, push and deploy the actual configuration through Morph.
Have you tried https://github.com/elitak/nixos-infect ? Works like a charm (with DO). It's a oneliner, you don't need to fiddle with anything. If it won't work from the user config option, just paste it in the live VPS and it will rebuild itself.
Morph is another great alternative to NixOps (well, it's not a replacement per se, but it's easier to use and lightweight in comparison to NixOps). It's basically just a really nice wrapper that allows you to easily deploy smaller herds of servers (~100 and less). I wholeheartedly recommend trying it out https://github.com/DBCDK/morph
Have you seen https://github.com/elitak/nixos-infect ? It allows you to easily re-create/infect existing distros into NixOS. Super helpful, works as a charm (tested on DO).
I'm actually aiming to do that in a series of post in the upcoming month(s)... I've started with a noob-friendly (written by a noob!) introduction and plan to continue with installer, basic package creation, module creation, discussing how to do rollback, what are generations etc. etc. ... I did some presentations on NixOS and these topics so I'd like to distill that into a short and easy to grasp blog posts @ https://nixos.online - feedback is more than welcome!
Maybe I could also include my own cheatsheet, which is refurbished version of the "official" one, but just for the basic commands in direct comparison to Debian-like distros.
"To Henry Kissinger"