I did some other tests:
on my system:
- I removed all noto fonts + font cache reindex
- test inkscape -> fonts preview ok
- I edited ~/.config/gtk-3.0/settings.ini and changed line "gtk-font-name" with
another existing font (for example Arundina)
"gtk-font-name=Noto Sans 10" -> "gtk-font-name=Arundina Sans 10"
- test inkscape -> problem
- with "gtk-font-name=nonexistentfontname"
- test inkscape -> fonts preview ok
- with a different existing font "gtk-font-name=Dejavu Sans Mono 10"
- test inkscape -> problem
- I reinstalled all fonts noto
- I commented line: "#gtk-font-name=Noto Sans 10"
- test inkscape -> fonts preview ok
on a fresh debian install (debian 10.4):
- I installed desktop xfce4 and plasma/kde
- I activated sid repository and installed inkscape + reboot
- I am logged in to the xfce4 desktop
- test inkscape -> fonts preview ok
- I created file ~/.config/gtk-3.0/settings.ini with "gtk-font-name=Noto Sans 10"
- test inkscape-> fonts preview ok
- I am logged in to the plasma/kde desktop
- test inkscape (file setting.ini is already present) -> problem
- I removed font name "gtk-font-name="
- test inkscape -> ok
- I inserted another existing font (for example Gentium) "gtk-font-name=Gentium 10"
- test inkscape -> problem
from the tests it would seem that the problem occurs from the combination:
debian/sid + plasma/kde + config gtk-font-name (indicating any existing character)
if can help...
Antonio