General problems with jekyll back-end

We are increasingly facing issues with jekyll and the plugins we need, some of which unmaintained.
This has reached the point where every time I want to build the website locally, I need to debug first.

The problems dependencies of the website are as follows:

* `jekyll-sass-converter`, a core dependency of `jekyll`, either depends on the broken sassc ruby or on google-protobuf, which fails to compile on systems that use link-time optimization by default such as Arch or Fedora. This is an unfixed long-known issue with the gem.
* `jekyll-algolia` has been abandoned by algolia.
* `jekyll-last-modified-at` depends on `posix-spawn` which is unmaintained and needs to be patched via a PR.
* `open-uri` from the citation generator depends on `stringio` which occasionally fails to compile on some systems.