Cura Version

5.11.0

Operating System

elementary OS 8.1 (Built on Ubuntu 24.04.3 LTS)

Printer

Ultimaker 3

Reproduction steps

1. Install Cura through Flatpak (or probably AppImage)
2. Try clicking Open in Cura on thingiverse.com or opening .stl file.

Actual results

Cura is not suggested.

Expected results

It suggests opening the file with Cura.
Just like OrcaSlicer or PrusaSlider (also installed as Flatpaks)

Add your .zip and screenshots here ⬇️

The .desktop file in this repo seems to include a valid and complete .desktop file with MimeType:
https://github.com/Ultimaker/Cura/blob/main/packaging/AppImage/cura.desktop.jinja#L12
But downloading the current 5.11.0 AppImage and inspecting squashfs-root/com.ultimaker.cura.desktop shows it only contains basic metadata (Name, Exec, Icon, Categories) and no MimeType. The Flatpak manifest on Flathub copies that desktop file verbatim before adjusting the Exec/Icon:
https://github.com/flathub/com.ultimaker.cura/blob/master/com.ultimaker.cura.yml#L24-L33
So the exported com.ultimaker.cura.desktop on users’ systems similarly lacks MIME/URI associations. As a result, GNOME portals report “No installed apps can open x-schema-handler/cura type” when Firefox tries to hand off downloads

Steps to inspect .desktop file in AppImage:

1. Download UltiMaker-Cura-5.11.0-linux-X64.AppImage from the release page.
2. Run ./UltiMaker-Cura-5.11.0-linux-X64.AppImage --appimage-extract com.ultimaker.cura.desktop.
3. Inspect com.ultimaker.cura.desktop.

What it looks like for me:

[Desktop Entry]
X-AppImage-Arch=x86_64
X-AppImage-Version=5.11.0
X-AppImage-Name=UltiMaker Cura
Name=UltiMaker Cura
Exec=UltiMaker-Cura
Icon=cura-icon.png
Type=Application
Terminal=false
Categories=Utility;
Comment=

The only part that seems to influence the .desktop file is the following Python script, but it only seems to fill in the {{ cura_version }}.
https://github.com/Ultimaker/Cura/blob/main/packaging/AppImage/create_appimage.py#L52-L59

I don't understand what happened to the .desktop file in the AppImage? Is there a step I'm missing?