Adding a Non-Steam Game that is also a flatpak

**Game information**

RetroArch

**Distribution name and version where applicable**

Fedora Release 32

**Flatpak info**

Flatpak 1.6.5
default
host

**Problem description**

Adding a non-steam game that is a flatpak can't be found. I'm specifically trying to add RetroArch that is a flatpak. Steam is looking for a .desktop file. Is there a way to show visibility in the sandbox?

**Does this issue reproduce with native Steam**

Have not tested likely not

Start by reproducing the issue described with RetroArch as a Flatpak on Fedora 32 using Flatpak 1.6.5, and check whether its .desktop file is visible to Steam in the sandbox. Review the issue comments and any available logs before deciding what behavior is expected; done means Steam can find and add the Flatpak game.

Written by the indexing model from the issue text.