Not a search engine, but last week I learned of the European Open Websearch project, which builds a new free and open search index. It should already be ready to try out. Hopefully we will see some search engines implementing this soon.

Thought I would mention Guix. I don’t know about using it as an OS but just the package manager is so nice to build reproducible software environments (although disclaimer I discovered this myself a few weeks ago). At least as close you can get without including proprietary hardware drivers. Building MPI applications on my laptop and moving them to an HPC cluster with full performance feels like magic.