GNOME 48 switched to new Inter and Iosevka based Adwaita fonts:067cb4b155https://blogs.gnome.org/monster/introducing-adwaita-fonts/ The default fonts were last changed to Cantarell and Source Code Pro in GNOME 3.32:965062de47Source Sans was added alongside them inc99a666aacbut it does not seem to be needed nowadays. The only relevant package mentioning it according is GNOME Recipes: https://codesearch.debian.net/search?q=Source+Sans+-pkg%3Atexlive+-pkg%3Aopenjdk+-pkg%3Abootswatch+-pkg%3Aqt%28%5Cd-%29%3Fwebengine+-pkg%3Afirefox+-pkg%3Ar-cran+-pkg%3Ataskflow+-pkg%3Afonts-adobe-sourcesans+-path%3Asvg%24+-path%3A%2Fdoc%2F+-path%3A%2Fdocs%2F&literal=1 DejaVu fonts are meant as a generic fallback but they are already pulled in by `fonts.enableDefaultPackages` option.