Glad they made a blog post about this, I saw the support start to crop up a little bit ago.
It seems that GitHub used Determinate Systems’s Zero to Nix has the link for flakes, which isn’t an official source (afaik, and looking on Flakes - Official NixOS Wiki)
This is much simpler than the basic GitHub action I have been using in my repo.
I like that it splits different inputs into their own PRs.
This + Hydra + Mergify in my case is really useful for my automatic update workflow on my personal infra and software repos.
Cool! Now I can get Dependabot Spam Alerts for Nix too. 
I guess whoever wrote it reads discourse, because it’s been updated!
People brought it up in the issue: Nix flake support · Issue #7340 · dependabot/dependabot-core · GitHub
Hi, I built this. And yes, I read Discourse 
Thanks to those who pointed out the zero-to-nix link in the changelog post. I didn’t write the post myself, but I should have caught that before it went out. It now points at the NixOS wiki.
I also did the nix support in Renovate back in 2022, so I’ve been wanting to bring this to Dependabot for a while.