Flatpak integration whit other applications

Please help me whit this

Is there a way to make a Flatpak package talk to another application (Flatpak or not)?
Let me give you some examples to be clearer.

Example 1: I would like to integrate Mendeley (Flatpak) with LibreOffice (Flatpak);

Example 2: I would like to integrate QGIS (Flatpak) with GRASS (native).

In ‘Example 1’, Mendeley installs an extension in LibreOffice to manage bibliographic references.
In ‘Example 2’, GRASS provides plugin and algorithms for QGIS.

I do not see how to solve ‘Example 1’ without performing this interaction.
‘Example 2’ can be solved by packing GRASS next to QGIS, but that’s another story.

AFAIK the preferred way to do this is by sending D-Bus messages to the other application, maybe using D-Bus activation.

This is one of the (many) limitations of Flatpak. I would suggest installing
the software as native if they don’t currently use Portals or D-Bus.

It’s not really a limitation of Flatpak if applications aren’t talking to each other using “proper” IPC methods.

First of all, there are “proper” IPC methods other than D-Bus.

Regardless, many of these require loading a .so into the host, or a language-
specific module. That’s just not possible with Flatpak with security settings

Actually it does have an extension system in place for situations that require loading shared objects and the like, which is used by sdk extensions.