The game automatically minimizes when changing focus

**Game information**

Team Fortress 2 (Only happens on full screen)
Not tested with other games.
Tested with steam's big picture, it doesn't happen.

**Distribution name and version where applicable**

Fedora 33 Workstation Edition
GNOME 3.38.3

**Flatpak info**

Flatpak 1.10.1
default
host

**Problem description**

The issue is every time I change focus (like opening another window or changing workspace), it turns into a window and minimizes itself. When I click on the window again on the GNOME Overview, it returns to the original state.

It is not a really big issue overall, but it is a minor annoyance.

**Does this issue reproduce with native Steam**

No, it only happens on the Flatpak version.

Reproduce the issue with Team Fortress 2 in the Flatpak Steam client on Fedora 33 with GNOME 3.38.3, using fullscreen mode and changing focus or workspace. Compare the behavior with Steam Big Picture and native Steam as described. Done means identifying the cause and preventing the game from becoming windowed and minimized when focus changes.

Written by the indexing model from the issue text.