I had to temporarily remove #Emacs & #Labplot from my config to get to properly rebuild my system (and to be able to keep updating my #NixOS config). Emacs built-in org-mode package seemed to be missing, and Labplot had a compilation error.

We're a few days from the release of NixOS 25.11, I can't help but think it's related. I might be wrong but if it is (related), it's a hell of a bad signal for stability (I'm running NixOS stable through flakes).