Comment # 5 on bug 1118032 from Patrick Finie

(In reply to Patrick Finie from comment #4)
> I did not want to add yet another repository to the long list of
> repositories already enabled.  What i ended up doing is forced a downloaded
> version of the .ttf into the directory and then had to rename the .ttf to
> over write the old broken font.  Once this was done Calibre opened and
> worked with no error or issue.

~/bin> calibre
qt5ct: using qt5ct plugin
qt5ct: D-Bus global menu: no
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
qt5ct: D-Bus system tray: no


So it was just one broken ttf as Malcomlewis from #suse thought it would be.