OK. I maybe can try to add a fontconfig script or something like that.
If you want to keep them in place, a fontconfig "script" as simple as <?xml version="1.0"?> <!DOCTYPE fontconfig SYSTEM "fonts.dtd"> <fontconfig> <dir>/usr/share/javascript/mathjax/fonts/HTML-CSS/TeX/otf</dir> </fontconfig> will be sufficient, if dropped into '/etc/fonts/conf.d'. - Fabian