Since some time now the Steam Flatpak cannot start up and I have no idea why this happens.

Web research leads to basically nothing that is related to what I experience so I assume it has something to do with my system. Other Flatpaks start up normally and I can use them.

When resetting everything related to the Steam Flatpak and reinstalling it from Flathub it loads and installs the Flatpak and then installs all necessary stuff

[various update-related stuff]
setup.sh[4598]: Forced use of runtime version for 32-bit libcurl.so.4
setup.sh[4598]: Found newer runtime version for 32-bit libSDL2-2.0.so.0. Host: 0.2400.0 Runtime: 0.2600.5
setup.sh[4598]: Forced use of runtime version for 32-bit libgtk-x11-2.0.so.0
setup.sh[4598]: Found newer runtime version for 32-bit libvulkan.so.1. Host: 1.3.224 Runtime: 1.3.239
setup.sh[4598]: Forced use of runtime version for 32-bit libdbusmenu-glib.so.4
setup.sh[4598]: Forced use of runtime version for 32-bit libcurl-gnutls.so.4
setup.sh[4598]: Forced use of runtime version for 32-bit libdbusmenu-gtk.so.4
setup.sh[4598]: Forced use of runtime version for 64-bit libcurl.so.4
setup.sh[4598]: Found newer runtime version for 64-bit libSDL2-2.0.so.0. Host: 0.2400.0 Runtime: 0.2600.5
setup.sh[4598]: Found newer runtime version for 64-bit libvulkan.so.1. Host: 1.3.224 Runtime: 1.3.239
setup.sh[4598]: Forced use of runtime version for 64-bit libcurl-gnutls.so.4
steam.sh[2]: Steam client's requirements are satisfied

So everything looks good up to this point. The small Steam update windows poppend up several times indicating the running installation/update. The output then continues:

[2023-08-17 22:47:50] Startup - updater built Jul 28 2023 18:44:09
[2023-08-17 22:47:50] Startup - Steam Client launched with: '/home/dirk/.var/app/com.valvesoftware.Steam/.local/share/Steam/ubuntu12_32/steam' '-no-cef-sandbox'
08/17 22:47:50 Init: Installing breakpad exception handler for appid(steam)/version(1690583737)/tid(5467)
[2023-08-17 22:47:50] Loading cached metrics from disk (/home/dirk/.var/app/com.valvesoftware.Steam/.local/share/Steam/package/steam_client_metrics.bin)
[2023-08-17 22:47:50] Failed to load cached hosts file (File 'update_hosts_cached.vdf' not found), using defaults
[2023-08-17 22:47:50] Using the following download hosts for Public, Realm steamglobal
[2023-08-17 22:47:50] 1. https://cdn.steamstatic.com, /client/, Realm 'steamglobal', weight was 1, source = 'baked in'
[2023-08-17 22:47:50] Verifying installation...
[2023-08-17 22:47:50] Verification complete
XRRGetOutputInfo Workaround: initialized with override: 0 real: 0xf0d328f0
XRRGetCrtcInfo Workaround: initialized with override: 0 real: 0xf0d311c0
GetWin32Stats: display was not open yet, good
GetWin32Stats: display was not open yet, good

(The last line gets printed twice, yes.)

The first startup process then hangs there for a few seconds and continues with this.

steamwebhelper.sh[5473]: Running under Flatpak, disabling sandbox
steamwebhelper.sh[5473]: CEF sandbox already disabled
CAppInfoCacheReadFromDiskThread took 0 milliseconds to initialize
src/steamUI/steamuisharedjscontroller.cpp (540) : Failed creating offscreen shared JS context
src/steamUI/steamuisharedjscontroller.cpp (540) : Fatal assert; application exiting
08/17 22:48:39 Init: Installing breakpad exception handler for appid(steam)/version(1690583737)/tid(5467)
assert_20230817224839_27.dmp[5771]: Uploading dump (out-of-process)
/tmp/dumps/assert_20230817224839_27.dmp
dirk ~ $ 

After the command prompt is shown agein, this gets printed:

assert_20230817224839_27.dmp[5771]: Finished uploading minidump (out-of-process): success = yes
assert_20230817224839_27.dmp[5771]: response: CrashID=bp-f62fb7e8-d024-452e-a937-9c6672230817
assert_20230817224839_27.dmp[5771]: file ''/tmp/dumps/assert_20230817224839_27.dmp'', upload yes: ''CrashID=bp-f62fb7e8-d024-452e-a937-9c6672230817''

At the given location there is no dump file.

Do you guys have any Idea why this happens and how I can fix it?

Involved software:

$ flatpak --version
Flatpak 1.15.4

$ flatpak remotes
Name    Optionen
flathub system

$ flatpak info com.valvesoftware.Steam | grep Version | awk '{print $2}'
1.0.0.78

$ uname -rms
Linux 6.4.10-arch1-1 x86_64

$ openbox --version | head -n1
Openbox 3.6.1

$ pacman -Qi xorg-server | grep Version | awk '{print $3}'
21.1.8-2