Firefox has just updated and now it doesn't see userChrome.css, toolkit.legacyUserProfileCustomizations.stylesheets is set to true. I'm trying to hide the scrollbar by
html {
scrollbar-width: none !important;
}
and everything worked fine before firefox updated.
I've put the chrome/userChrome.css to every profile folder I have and restarted firefox every time, but it still doesn't see anything from userChrome.css
--
UDP:
Firefox still doesn't see my custom css, but if you want to hide the scrollbars, this addon works.