Comment 15 for bug 1856624

(In reply to David Lechner (:dlech) from comment #8)
> More info: https://askubuntu.com/questions/1076412/firefox-freezing-with-100-cpu-usage-for-30-seconds-when-launching-chromium

Thank you for the links. One of the discussion comments suggest the following to also trigger the CPU burning in FF:

    mkdir -p ~/.fonts/Library/ && touch ~/.fonts/Library/

That actually works for me, *without* starting any libchromiumcontent app, so it's indeed due to fontconfig.

I just installed fontconfig+libfontconfig1 2.13.1-2ubuntu2 (the disco packages work on bionic), and that majorly reduces the problem. If Firefox has several tabs opened, there is still a spike that can be seen in CPU usage when libchromiumcontent starts (or with touch ~/.fonts/Library/), but its now only around 1 second, so you have to look for it to notice.