Ok, I fixed it. I did a huge bulk install of fonts using your "in home but not in workstation" list, and it fixed the issue, at least for Youtube anyway. Here is the list of what did install. I do know that Youtube use the roboto font, which is on this list, but I did not test a separate install, though. Can you try it ?
Installed fonts : fonts-3270 fonts-aoyagi-kouzan-t fonts-aoyagi-soseki fonts-arabeyes fonts-arphic-ukai fonts-arphic-uming fonts-beng fonts-beng-extra fonts-cabinsketch fonts-century-catalogue fonts-circos-symbols fonts-cmu fonts-cns11643-kai fonts-cns11643-sung fonts-cwtex-docs fonts-cwtex-fs fonts-cwtex-heib fonts-cwtex-kai fonts-cwtex-ming fonts-cwtex-yen fonts-dancingscript fonts-dejima-mincho fonts-deva fonts-deva-extra fonts-dosis fonts-farsiweb fonts-freefarsi fonts-gargi fonts-gubbi fonts-gujr fonts-gujr-extra fonts-hack-otf fonts-hack-ttf fonts-hack-web fonts-humor-sans fonts-indic fonts-ipaexfont fonts-ipafont fonts-johnsmith-induni fonts-junction fonts-kalapi fonts-knda fonts-lohit-beng-assamese fonts-lohit-beng-bengali fonts-lohit-deva fonts-lohit-gujr fonts-lohit-knda fonts-lohit-mlym fonts-lohit-orya fonts-lohit-taml fonts-lohit-taml-classical fonts-lohit-telu fonts-maitreya fonts-mikachan fonts-mlym fonts-moe-standard-kai fonts-moe-standard-song fonts-mononoki fonts-nakula fonts-nanum-extra fonts-navilu fonts-orya fonts-orya-extra fonts-pagul fonts-roboto fonts-rufscript fonts-sahadeva fonts-samyak-deva fonts-samyak-gujr fonts-samyak-mlym fonts-samyak-taml fonts-sarai fonts-smc fonts-taml fonts-telu fonts-telu-extra fonts-ubuntu-font-family-console fonts-ukij-uyghur fonts-vlgothic fonts-vollkorn fonts-wqy-zenhei -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1672698 Title: Broken/Missing font rendering in firefox To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1672698/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs