Since I upgraded to Ubuntu 18.04, Okular doesn't follow the Adwaita-dark or Arc themes when I set them with the Gnome tweak tool. Is there any way to fix this? All I really want is for Okular to use dark colors for its menus and toolbars.
Edit: When I try
from the terminal, I get a bunch of errors like
(okular:16699): Gtk-WARNING **: 22:58:15.581: Theme parsing error: gtk.css:137:54: Using one color stop with linear-gradient() is deprecated. (okular:16699): Gtk-WARNING **: 22:58:15.587: Theme parsing error: gtk.css:1839:9: Expected a string. (okular:16699): Gtk-WARNING **: 22:58:15.590: Theme parsing error: gtk.css:2913:17: Using Pango syntax for the font: style property is deprecated; please use CSS syntax
I've also tried downloading systemsettings and kde-config-gtk-style and activating the themes there, with no response.