that’s because you are not running the plasma desktop environment, which i assumed you were.
sorry for the confusion, hope you can sort it out.
thanks, it makes a lot more sense now.
@dzon That menu I can find! But mine has none of your choices:
The ones I’ve tried didn’t change my problem.
I’ve searched the web and found no clues how to install more plugin styles. Sorry for my ignorance, I’m not a Debian person - it just came with the RasPi.
Sorry for the delay - this site only lets me include one image per post, and then shames me for posting too many times, and then locks me out for an hour between posts…
First of all, I’m kinda lost here what desktop you’re actually running. Arch, Debian, Pi…? In either case, I’m guessing we’re talking about a gtk based desktop and I’m thinking lxde, right? In order to get Qt apps to have a , more or less, uniform look on gtk desktops, you’ll need qt5ct AND the qt5-style-plugins. Trust me ( or don’t), if you don’t install those, there’s a very good chance it will not work. If you can’t find those packages in the package manager of whatever you’re running…well…
If you DO have them, install them, log out/in. Open the qt5-ct ( that configuration app) and set it to use gtk. That option mostly works. If it doesn’t, try a few. But normally it should.
In the case it STILL doesn’t work, there’s another option you could try and that is to run Okular in kvantum. In order to do that, you’ll need to install kvantum first. If you install the qt5-style-kvantum, it’ll install a couple of kvantum themes as well.
Log out/in in order to have kvantum as an option in the qt5ct.
How that will look like will depend on the kvantum theme which is used. In order to set that, you’ll need to set it in the kvantum manager.
At which point you can choose an installed theme to be applied.
If none of this still doesn’t work, I suggest you try to dig up a solution on the rasp forums. Because from what I know, Pi Os comes with MOST of the recommended software. That doesn’t mean ALL.
And um…on a sidenote. If you are indeed running lxde, wayland is a very bad choice for openbox.
RasPi used to have “Raspbian” versions, but the 5 seems to have standard Debian Bookworm. Mine seems to have GTK 4.8.3, with wlroots (-) (I have no idea what that is…), Wayland, and lightdm. I have qt5ct, and qt5-style-plugins 5.0.0 installed.
Open the qt5-ct ( that configuration app) and set it to use gtk.
The only gtk option is gtk2, which was selected when I first saw the screen.
So:
pi@raspberrypi:/ $ sudo apt install kvantum
…
E: Unable to locate package kvantum
pi@raspberrypi:/ $
pi@raspberrypi:/ $ sudo apt install qt5-style-kvantum
…
Setting up qttranslations5-l10n (5.15.8-2) …
Setting up qt5-style-kvantum-themes (1.0.7-1) …
Setting up qt5-style-kvantum (1.0.7-1) …
Setting up qt5-style-kvantum-l10n (1.0.7-1) …
Processing triggers for desktop-file-utils (0.26-1) …
Processing triggers for hicolor-icon-theme (0.17-2) …
Processing triggers for gnome-menus (3.36.0-1.1) …
Processing triggers for mailcap (3.70+nmu1) …
pi@raspberrypi:/ $
Now there are lots of Okular color options, and all the menu items are at least tolerably visible.
Maybe if I try enough of them I’ll find one I actually like…
Thank you for that suggestion! I think I can move on to other problems now.
Oh…
Wayland was the default for the RasPi 5, they have a blog post on how wonderful it it. I wasn’t aware of any lxde here, but it looks like there is some:
/etc/xdg/openbox/LXDE
/etc/xdg/lxsession/LXDE
/etc/xdg/pcmanfm/LXDE
/etc/xdg/lxpanel/LXDE
/usr/share/doc/lxde
/usr/share/lxde
Is that really a problem?
https://forums.whonix.org/t/lxde-wayland-support/17388
Apparently that wlroots is my Desktop Environment. Hopefully the RasPi devs know what they are doing…
So, I was right, you’re using lxde ( which is the desktop environment). It uses
openbox as window manager. Lightdm is your login manager. Of the so-called desktop environments ( lxde, lxqt, xfce, gnome,kde…), lxde is a gtk based lightweight ( low on resources and quick) one. So, you’re absolutely fine for that matter. Now, since you have the neccesary qt5 packages installed and qt5ct is set to gtk, okular should theoretically use your overall gtk theme which is set in lxappearance ( see picture) Make sure you set everything as should in the qt5 manager. If that still isn’t the case, then yes, as mentioned, kvantum is an option. But um…lxde works best in X11, not wayland. Openbox was never designed for it. Those Raspberry dudes oughtta know that. You should be able to log into an X11 session in lightdm.
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On a sidenote. Imho, you will be far better off running lxde on a linux distribution like Debian. The rig doesn’t have to be much since lxde can practically run on coal so to speak. A healthy hd or ssd, 6 gigs of ram and you’re good to go. I’ve been using openbox for two decades and ran openbox setups on debian that booted well under 100 mb. It’s rocksolid and will probably survive a nuclear blast. A Debian/Lxde combo will provide a clean, snappy and very stable experience. Imho that is.
Here’s such an example of openbox on debian. Not strictly lxde as desktop environment but…just so you know you don’t need much to get a proper computer…with Okular 
Especially…I ran a live debian lxde iso to check. Since it’s live I can’t use the qt5ct so I’ve set okular to use a kvantum theme. Both Gtk as Kvantum are Arc Dark.
Just a note on what I learned today…
Since 2024-10-28 RPiOS now has three* possible desktop configurations: X11/lxde, Wayland/Wayfire, or Wayland/labwc. They all use different methods to configure things that run at desktop start though the differences between lxde and labwc are more subtle than the differences between either of those and wayfire.
Wayland/labwc is the default on all new installations of RPiOS with desktop on all Pi models after this date.
So I’m not on lxde since that update. And wlroots is the basis for labwc. Apparently Wayland/Wayfire really didn’t work out well for RasPi. Supposedly labwc is faster and solider…
Labwc is a stacking/compositing manager. It’s available as an option on core openbox distros like Bunsenlabs. But it’s not really there yet. Moreover, you need some experience using it. But, whatever you like…you like.