A few days ago, most fullscreen games launched via Steam began showing the title bar no matter what settings I have configured. I am not sure what would have changed to cause this to start happening. It seems that games running with proton work as expected, but games with native linux clients show the title bar.
Screenshot of example

I am running a 3 monitor set up (left=1920x1080, center=3840x2160, right=3840x2160) running with a GeForce RTX 2070 Super on the Nvidia v455 drivers.

:~$ xrander



Screen 0: minimum 8 x 8, current 9600 x 2160, maximum 32767 x 32767

DP-0 disconnected (normal left inverted right x axis y axis)

DP-1 disconnected (normal left inverted right x axis y axis)

HDMI-0 connected 1920x1080+0+451 (normal left inverted right x axis y axis) 521mm x 293mm

   1920x1080     60.00*+  59.94    50.00  

   1680x1050     59.95  

   1440x900      59.89  

   1440x576      50.00  

   1440x480      59.94  

   1280x1024     75.02    60.02  

   1280x960      60.00  

   1280x720      60.00    59.94    50.00  

   1152x864      75.00  

   1024x768      75.03    70.07    60.00  

   800x600       75.00    72.19    60.32    56.25  

   720x576       50.00  

   720x480       59.94  

   640x480       75.00    72.81    59.93    59.94  

DP-2 connected primary 3840x2160+1920+0 (normal left inverted right x axis y axis) 600mm x 340mm

   3840x2160     60.00*+  30.00  

   2560x1440     59.95  

   1920x1080     60.00    59.94  

   1600x900      60.00  

   1280x1024     60.02  

   1280x800      59.81  

   1280x720      60.00    59.94  

   1152x864      59.96  

   1024x768      60.00  

   800x600       60.32  

   720x480       59.94  

   640x480       59.94    59.93  

DP-3 disconnected (normal left inverted right x axis y axis)

DP-4 connected 3840x2160+5760+0 (normal left inverted right x axis y axis) 600mm x 340mm

   3840x2160     60.00*+  30.00  

   2560x1440     59.95  

   1920x1080     60.00    59.94  

   1600x900      60.00  

   1280x1024     60.02  

   1280x800      59.81  

   1280x720      60.00    59.94  

   1152x864      59.96  

   1024x768      60.00  

   800x600       60.32  

   720x480       59.94  

   640x480       59.94    59.93  

DP-5 disconnected (normal left inverted right x axis y axis)

USB-C-0 disconnected (normal left inverted right x axis y axis)

As mentioned, a few days ago I was able to run games full screen as expected.
Things I've tried:

• Downgrading the nvidia drivers to version 450


• Launching with the '-fullscreen' launch option


• Setting nvidia_drm modeset=1


• Forcing Composition Pipeline


• Enabling 'auto-hide dock' as suggested by RingGamesCompany

I am out of ideas. If anyone with more experience than I has any ideas, or if there's any additional information I can supply, I'm happy to do so.