It also has nothing to do with display server. This is ubuntu wayland session, same bug.
** Attachment added: "Screencast from 04-19-2020 12:17:48 AM.webm" https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1872844/+attachment/5356587/+files/Screencast%20from%2004-19-2020%2012%3A17%3A48%20AM.webm -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to firefox in Ubuntu. https://bugs.launchpad.net/bugs/1872844 Title: Changing theme Light<->Standard preserves theme for Firefox title bar (in Xorg sessions) Status in firefox package in Ubuntu: Confirmed Bug description: This is Ubuntu 20.04 beta. Start a program that has title bar. Try Firefox or whatever. Then navigate to settings->appearance. Now set the theme to Standard, then Light - Firefox will now have white theme with dark titlebar. Setting to Dark resets the bug. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1872844/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp