gnome-software supports installing a number of non-application things, which could be classified as OS extensions: fonts, input methods, codecs, translations, etc. The rpm-ostree plugin should support installing these things via package layering.
https://github.com/projectatomic/rpm-ostree/issues/1224 is where the necessary rpm-ostree api is discussed
upstream issue https://gitlab.gnome.org/GNOME/gnome-software/issues/342
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