Couldn’t find the project in my browser history or Lemmy saves. I’m pretty sure it was Lemmy though that led me to find a GitHub project similar to OSTree. It sounded like it was maintained by one person and it hasn’t been updated in a long time because the author thought it was “done” and they used it frequently.
It was a tool that let them basically create images that could be booted from and it was easy to layer software on top of a base image and I think there were config files similar to Containerfiles but didn’t look the same. Don’t think it be was “goldboot” either but that might be a little closer to what the project does. I don’t think it was something Fedora specific either like bootc.
Update: Found it! It was in the history of a laptop I rarely use (of course). The project is https://github.com/godarch/darch and it does appear to be those things I said: layered, docker-like, bare metal, and OS agnostic.
I’m going to assume it’s not Universal Blue… But parts of your description reminded me of it.
Could’ve been something Fedora-ish but based on the GitHub I don’t think that’s it. The most distinct thing I remember is that it appeared abandoned but the author just didn’t feel it needed any changes.
I use like four different devices to browse and some have multiple browsers so checking history has been rough.