This problem is annoy me for a long time, but now i want to fix that finally. The problem is some Roboto fonts is not visible on pages.
I tried reinstall system (all except /home is new) several times (changing distros), but problem still exists.
In Chrome this issue is missing, he's rendering all as it must be.
I also tried to remove Roboto font from system completely, I tried to reinstall it. It's fixed just part of the problem.
This is how Amazon S3 control panels looks like to me.
Inspecting says the interface uses Roboto-Bold font from sytem, but i haven't Roboto-Bold font in the system. Why did he try to load it from system, not from web? This is the problem i see.
If i remove Roboto font from system, the most of the sites, which uses 'Roboto' is also come blank. F.e. YouTube will be completely white with pictures. For now on YouTube only tooltips has the problem.
How can i remove Roboto from system correctly or fix missing font. I tried to remove $HOME/.mozilla folder, but no results. As I say, this problem is only in FireFox, all Roboto fonts from system works perfectly in Chrome, LibreOffice, Inkscape and other programs.
My distribution KDE Neon, but this problem present in Ubuntu, Kubuntu and other distros i tried.