Manjaro’s manjaro-gnome-settings contains /usr/share/glib-2.0/schemas/99_manjaro-settings.gschema.override, which attempts to override
[org.gnome.gedit.preferences.editor]
auto-indent=true
editor-font='Hack 12'
scheme='solarized-dark'
tabs-size=4
use-default-font=false
However, for gedit 48, it was changed in commit theme-variant: have two GSettings keys for the style-scheme (f7dc3953) · Commits · World / gedit / gedit · GitLab.