Flatpak apps do not respect GTK theme on Wayland (Kubuntu 23.10)

[Samuel R]

On Wayland, GTK apps doesn't respect the theme that is selected through gsettings. This didn't happen before on Kubuntu 23.04, so it seems to be a regression. Flatpak gtk apps need xdg-desktop-portal-gtk to access dconf settings, which it can't do, due to the portal not working properly. This also affects fonts and cursor themes, where they are also not respected. This issue doesn't seem to happen on X11. Version 1.15 of xdg-desktop-portal-gtk appears to fix the issue.

What I expected to happen:
The xdg-desktop-portal-gtk would work and gtk flatpak apps would respect the theme of my desktop on Wayland

What happened instead:
Gtk flatpak apps do not respect my desktop theme, cursor or fonts on wayland

Ubuntu Version: Kubuntu 23.10
Package Version: 1.14.1-1

[Samuel R (gamertechuniverse)]

It appears that adding a line to /usr/share/xdg-desktop-portal/kde-portals.conf fixes the issue. This should be added to the xdg-desktop-portal-kde package, which the file belongs to.

[preferred]
default=kde
+ org.freedesktop.impl.portal.Settings=kde;gtk;

[Jeff (jeff09)]

Thank you for the fix, it's much appreciated after the 23.04 -> 23.10 update presented this quite heavy regression.

Just restarting affected programs didn't show a change, so ended up running:
```
systemctl --user restart xdg-desktop-portal
systemctl --user restart xdg-desktop-portal-gtk
```
Then after that the freshly opened programs behaved as expected again with decent looking fonts and the cursor behaving as expected depending on the context.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Rik Mills (rikmills)]

Thanks for the report. We will try to get this fixed as soon as practical. However, for now our priorities are still any issues on X11.

As per our release notes "A Plasma Wayland session is available for testing, but is not supported"

https://wiki.ubuntu.com/ManticMinotaur/ReleaseNotes/Kubuntu#Plasma_Wayland_session