Interestingly:
$ FC_DEBUG=256 fc-query /usr/share/fonts/truetype/ubuntu-font-family/Ubuntu-R.ttf | grep ast am(264) an(0) ar(36) as(64) ast(0) av(0) ay(0)
shows Asturian as having no missing codepoints; but it's possible that FontConfig is wrong here; for instance the "ar(36)" means that Arabic support will need coverage at 36 further codepoints.
Interestingly:
$ FC_DEBUG=256 fc-query /usr/share/ fonts/truetype/ ubuntu- font-family/ Ubuntu- R.ttf | grep ast
am(264) an(0) ar(36) as(64) ast(0) av(0) ay(0)
shows Asturian as having no missing codepoints; but it's possible that FontConfig is wrong here; for instance the "ar(36)" means that Arabic support will need coverage at 36 further codepoints.