I believe this is related to a recent update as yesterday night i was having no problems.
I can no longer build any latex file that specifies the use of any Source font (SourceSerif4, SourceSans3 and SourceCodePro)
trying kpsewhich SourceSerif4.otf doesnt output the file anymore
If configuration is any important here is the link to my config file for fonts, its on my nixos flake repo: modules/core/linux/config/fonts.nix · main · flakes / nixos · GitLab