Describe the bug
On a desktop, when using the Flatpak release of R2 with Flatpak Steam, the "Start Modded" and "Start Vanilla" buttons don't launch Steam.

To Reproduce
Steps to reproduce the behavior:
0. Have Flatpak Steam installed and R2 Modman installed as a Flatpak

1. Go to a game profile page
2. Click on "Start Modded" or "Start Vanilla"
3. Watch for errors/Steam not loading

Expected behavior
Steam to launch and load the game

Additional context
For me, when I click the button, I get this error: You are missing the following 32-bit libraries, and Steam may not run: libc.so.6. From what I can tell, this is because R2 Modman attempts to run steam.sh to launch Steam, which doesn't work to launch the Flatpak version (and is also where the 32-bit library error comes from).