There seems to be a qt5 branch on github: https://github.com/clementine-player/Clementine/tree/qt5.
Would this be an option?

What does it in practice mean if Julia doesn't like some libraries? Is there a way to fix this?

I didn't notice that at was abandoned. It is still mentioned on the tlp homepage and available in the repos of several major distributions, so I kind of assumed it was still an active project.

I should have checked that better, I'm sorry.

Ok, but isn't the size of the swap partition still a problem even after having it mounted at boot?
If I would gave let's say 10gb of my RAM used, 4gb of swap won't be enough to hibernate correctly if I understand this correctly.

I quickly want to note that the description is not really correct: Biber is a replacement for BibTeX (and works with BibLaTeX). One of the advantages over BibTeX is full UTF-8 support.