I think you can safely ignore that, that comes from Gtk3 library which complains about error in actual Gtk theme. Eventually you can change your Gtk theme in gnome-tweaks application.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1893021 Title: Flash plugin symbol lookup error with firefox 80.0+build2 on xenial (gtk_window_set_titlebar) To manage notifications about this bug go to: https://bugs.launchpad.net/firefox/+bug/1893021/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
