https://bugzilla.redhat.com/show_bug.cgi?id=2262410
--- Comment #17 from Łukasz Patron priv.luk@gmail.com --- (In reply to Oleg Oshmyan from comment #16)
libass uses Fontconfig's FcConfigSubstitute to convert mpv's "sans-serif" font name to a real font: https://github.com/libass/libass/blob/ 649a7c2e1fc6f4188ea1a89968560715800b883d/libass/ass_fontconfig.c#L286
Fedora's config says Noto Sans Arabic is the default sans-serif font:
{ alias="sans-serif", variable=true, family="Sans Arabic", obsoletes={ "sans-arabic-ui-vf" }, default=true },
Noto Sans Arabic does contain glyphs for European digits, so they are used.
What else could libass possibly do?
On the mpv tracker, OP also said he was seeing weird fonts in other applications besides mpv: https://github.com/mpv-player/mpv/issues/13396#issuecomment-1924131260
Yeah, the thing I noticed was that after Noto Sans update, KDE file picker rows got higher — https://imgur.com/a/6dBRYLg (before; after).