I have adopted this workaround:
copy gtk-3.0 specific setting to inkscape config subdir:
cp -a ~/.config/gtk-3.0 ~/.config/inkscape/
editing file ~/.config/inkscape/gtk-3.0/settings.ini
comment line:
; gtk-font-name=Noto Sans 10
modify command start application in:
XDG_CONFIG_HOME=/home/root/.config/inkscape inkscape
Now inkscape works, without making changes to the system.
However, I disabled the preview of the fonts because it takes too long.
Antonio