Variable fonts cause warnings
\version "2.25.6"
\paper {
property-defaults.fonts.serif = "Noto Serif"
}
\markup \bold "abc"
On a system where Noto Serif is shipped as a variable font (such as Fedora 38), this leads to warnings such as
warning: font index 393216 too large for font `/usr/share/fonts/google-noto-vf/NotoSerif[wght].ttf', using index 0
warning: font index 393216 too large for font `/usr/share/fonts/google-noto-vf/NotoSerif[wght].ttf', using index 0
See also https://lists.gnu.org/archive/html/lilypond-devel/2023-05/msg00046.html