[1000101]

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.

[elbear]

I haven't. I was trying to use nixos-generators, because at some point I want to generate a custom, stripped down image of NixOS. But until then, I might use nixos-infect, if it gets me a running instance of DO quicker.

[1000101]

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.

[elbear]

Didn't know about Morph. Thanks!