Evoland does not launch

**Game information**

[Evoland](https://store.steampowered.com/app/233470/Evoland/)

**Distribution name and version where applicable**

Fedora 30 x86_64

**Flatpak info**

```
$ flatpak --version
Flatpak 1.4.1
$ flatpak --gl-drivers
default
host
```

**Problem description**

The game never shows a window, crashing instantly.
dmesg shows no output.
When running steam with `flatpak run com.valvesoftware.Steam`, the following piece of log is observed:
```
sh: xmessage: command not found
Flash Player PPAPI not detected in /opt/google/chrome/PepperFlash/libpepflashplayer.so. Please install Chrome or edit config.js for another path
```
I tried `override --filesystem=/opt/google` but nothing changed (I have chrome installed), log still indicates the missinng "pepperflash" component.

**Does this issue reproduce with native Steam**

Not tested