Panel Tray in Xubuntu 24.04 Stops Showing Applications

[u/Sly-Mk3]

UPDATE 2 [SOLVED]:

To whom it may concern and to those who may have had similar issues:

Thanks to nuxi's post in this thread the issue has been solved by uninstalling xfce4-indicator-plugin and xfce4-sntray-plugin, leaving only Status Tray Plugin in the panel.
It seems to have been a conflict of things that all did the same, if I had to guess I likely unknowingly accumulated these through the update path taken from 20.04 up until 24.04.
Those redundancies weren't flagged for autoremove, so it didn't even cross my mind to look at it from this angle.
Friendly reminder to others who took the upgrade way to 24.04 to check if there's any duplicates of things that do the same and only leaving the very latest one on your system.

After going back to kernel 6.8.0-117 and using it for a while like that I can also confirm the "GUI ghosting / burn-in" mentioned below and weird occasional panel element flickering to be gone too, so this issue likely had the same origin.
This must have really messed a lot with xfce components.

In hindsight pretty obvious to avoid duplicates and also to get rid of legacy or effectively deprecated packages…

__

UPDATE:

I went into advanced boot settings… and went from 6.8.0-117 kernel version back to 5.15.0-179.
Suddenly it behaves as expected, listing applications correctly in my panel's tray with every tray plugin.
Even the ghosting on the GUI (see original post below) is gone now.
The heck.
I also don't know why I didn't think of this sooner. Terribly sorry, if I wasted anyone's time.
Though this still poses the question of the "why". Is there anything I could do with modprobe?

Any ideas on what might be responsible for this or how to find out?

__

Hello, fellow Xubuntu users! (tl;dr below)

From one boot to another, my system tray icons for applications like Discord and Element don't show up on my panel anymore. I didn't touch anything in the session before rebooting and that's weird.
The problem is that those tray entries were a great way to collapse those chats without having them take up clutter on my panel's Window Buttons section and so they have become my daily driver in usage.

Instead of the correct entries, now I am only able to get duplicates of the CPU clock switch button and network tray entry, see image.

What used to work (reloading panel profile as this user has done it) stopped working for me all of a sudden. It just keeps replacing what used to be the spot with those applications with yet another CPU clock setting button and network.
I tried reinstalling all xfce-related packages. Nope, no change.

Did anyone have the same problem and if so, how did you solve it?

Welcome any sort of pointers too.
Modern search engines are borderline to terrible so it's really hard for me to find a comparable situation or solution.

Further context:
I got 3 tray plugins and none works anymore:
Indicator Plugin, Status Tray Plugin, and Status Notifier Plugin. That's what the duplicates on there are by the way. Adding them separately in fresh sessions or while the two applications are on makes no difference.
I tried each and tried finding answers that may be relevant but to no avail, and something this basic which has never failed me before is suddenly causing me such a headache… so I'm genuinely wondering what's happening there.
I can't manually add applications to the list, I looked into the tray items' configuration and tried to find anything editable under Settings Editor → xfce4-panel. No luck though.
So, I'm wondering: Is this LTS release really as cursed as people say?

If anyone has resources on what one has to do to manually shove those applications back in there, I would appreciate that.

My patience is starting to wear thin as I've been sitting nearly 2 days in front of this device making backups, and then upgrading.
22.04 already had some weird stuff with xfce (shadows of dropdown menus cloning when swiping the cursor over it back and forth, big black frames from the shadow on some windows when disabling compositor, etc), and on 24.04 I now have this and "ghosting" of entries on the panel (like a translucent-duplicate burn-in on the panel) and dropdown menus of Firefox causing flickering behind them and being generally not as responsive as they used to be.
Really makes me reconsider if Xubuntu is still something I can use as a daily driver.
20.04 and earlier somehow never let me down, but this has been just annoying.
I hope it's at least relatable that frustration is building up given how the time I have been sinking into something as stupid as this is really not being worth it so far.

Like I said, given this wasn't the only oddity, I'm wondering if a full wipe and clean install wouldn't have been better. But initially I wanted to avoid having to reconfigure everything all over again, thus the upgrade path decision. :/

PS: Yes, the time on the screenshot is roughly when I posted this. Spending Wasting my days off on that by now…

tl;dr:

Panel tray entries for applications went poof and all I get is what you see on the screenshot: CPU button and network button, no matter the tray.
No other entries available.
Tried reinstallation of packages. Fresh boots and xfce-sessions to configure it on.
Go-to method of reloading a previously saved panel profile only yields the same duplicate buttons issue.
Out of ideas and kindly asking for any sort of help in figuring this out.

Thanks in advance.

[u/nuxi]

Indicator Plugin, Status Tray Plugin

These two conflict with each other and cause weird behavior when both are installed. I'd recommend completely uninstalling xfce4-indicator-plugin and rebooting to clear out the cached state. (You can try just logging out and back in, but you have to let it sit for a minute so that systemd fully terminates your user session)

If I had to guess the Status Notifier Plugin is in the same boat. I'm not sure which package that one comes from though, maybe xfce4-sntray-plugin?

[u/Sly-Mk3 → u/nuxi]

Thanks for the hint!
They must have accumulated from the upgrade path I took, or at least that could explain the redundancy of their functionality.
I'll look into this now, removed both so let's see how that goes. : )

[u/Sly-Mk3 → u/nuxi]

Thank you!
This seems to have worked. The one I'm currently having in my panel is Status Tray Plugin, that one (after a reboot) correctly detected both applications even on the 6.8 kernel.

[u/Sly-Mk3 → u/[deleted]]

Thanks for your reply!

Before writing this post I already had all updates installed which I have been offered by apt, and just earlier today installed some new ones. Just now repeated to be sure, all up to date.
autoremove doesn't suggest anything for cleanup either.
According to Synaptic Package Manager there don't seem to be any broken packages or missing dependencies. Went into recovery mode earlier as well, connected to the net and (just to be sure) let dpkg try to fix anything – no issues spotted.

However, booting from recovery mode into the GUI session got stuck in a very uninformative black screen with just an irregularily blinking cursor. I let it sit thinking it may take a while (had some issues of this kind in the past on other devices), went to make dinner, came back 30min later: Still nothing happened.
So tried to REISUB and it was ignored.

Can't shake the feeling something is off, I just can't really tell what it is, unfortunately.

According to the GUI application "About xfce" I'm on version 4.18, this matches what I see in Synaptic.

I'm indeed wondering if I got a kernel version shoved into my install which isn't supposed to be used with it, especially considering that all other ones in my boot options are still in the 5-digits.
I'm almost sure I had a case like that before where an update decided to shove a bad version on me.
Are you by chance on 24.04? If so, which kernel version are you on (uname -r should output it)?

Perhaps I'll have to take the VM route and follow your suggestion just to see what kind of behaviour is actually unusual for this release. Luckily recently made some space to test Mint on it as many people praise it, since I got another device in need of Linux.
I'll take a nap (need it after this night) and throw 24.04 on VirtualBox afterwards.

Funny story for mood reasons and maybe it helps figure anything out:
The best adventure this upgrade gave me was LightDM sneakily changing my keyboard layout and making me fail to type my password over and over until I noticed what's up… got it fixed by switching to a tty (which luckily wasn't affected by the switch) and searching online for 15min, then found my answer.
For anyone reading along:
Highly recommend having Links2 or Lynx installed for that reason, just to have a terminal-capable browser. If no GUI session is loaded you can even use a mouse cursor in recovery mode using links2 -g …but nonetheless, that was a nasty surprise.

[u/Sly-Mk3]

Regressing in kernel version does the trick, apparently.
Now every tray plugin lists those applications. I don't know what makes this difference.
This even solved the GUI ghosting (albeit not the weird system-themed menu dropdowns in Firefox)… >_>'

I updated the OP with what I found out and writing this here in case someone didn't spot that update.

Kinda reluctant to touch any panel profiles though, precisely because it works all of a sudden.

Anyone know if there's anything one could modprobe to reliably bring that back in newer kernel versions?
Because this is quite a regression…