Problems with XDG-Portals on GTK-based flatpak apps ?

[SpidFightFR]

Is this a new report?

Yes

System Info

Void 6.11.2_1 x86_64 AuthenticAMD uptodate rrmFFFFFFFF

Package(s) Affected

flatpak-1.15.10_2; xdg-desktop-portal-kde-6.1.5_1

Does a report exist for this bug with the project's home (upstream) and/or another distro?

I opened an issue here, on the base project's page. However since i noticed the upstream version works normally. I assume it's an issue with portals or flatpak, or i'm missing something entirely different here.

Expected behaviour

The "open-file" dialog window should open the proper dialog window, for example with kde:

Actual behaviour

The "open-file" window within a gtk-based app is supposed to open the portal's filepicker (e.g: the kde dialog window on kde).

However here it opens the default gtk dialog window.
And an error happens: Server is missing xdg_foreign support

Steps to reproduce

1. Open a gtk-based app (e.g: Webcord in my case, based on the electron framework, which uses gtk)
2. find a way to summon the "open-file" dialog, by uploading a file for example.
3. Issue happens.

NOTE: i'm absolutely not sure what causes the issue.

[SpidFightFR]

I saw a GTK update recently, can these event be related ?

[SpidFightFR]

Not linked to Voidlinux.