QDesktopServices::openUrl, under snap does not open local files

As the summary says, when running an app that was snapped, when you tell QDesktopServices::openUrl to open a local file (e.g ~/Documents/myDocument.pdf), nothing happens.

Opening a webpage works fine.

Maybe I'm missing something in snapcraft.yaml... In this case it should be documented.

I could reproduce running the attached project on Ubuntu 18.04

• compile in release (target folder build-release)
• open a terminal and run the script snapcreator/create_snap.sh to snap and prime the app
• to test outside snap, execute this command:
  <ProjectDir>../output/desktopservicesbug/usr/bin/desktopservicesbug.sh
• to test from snap, execute this command:
  desktopservicesbug