Your system information

• Steam client version (build number or date): 1526603471
• Distribution (e.g. Ubuntu): Fedora 29
• Opted into Steam client beta?: Yes
• Have you checked for system updates?: Yes

Please describe your issue in as much detail as possible:

Steam client sometimes crashed when I press "Play" button on game page in store which unsupported Linux.
For example this crash I reproduced when press "Play" button om this page: https://store.steampowered.com/app/359550/Tom_Clancys_Rainbow_Six_Siege/

Refresh r[0519/150816.036890:WARNING:render_frame_host_impl.cc(2751)] OnDidStopLoading was called twice.
ExecuteSteamURL: "steam://run/359550"
GameAction [AppID 359550, ActionID 24] : LaunchApp changed task to RequestingLicense with ""
GameAction [AppID 359550, ActionID 24] : LaunchApp failed with AppError_29 with ""
GameAction [AppID 359550, ActionID 24] : LaunchApp changed task to Failed with ""
AL lib: (WW) alGetError: Querying error state on null context (implicitly 0xa004)
Failed to open digital audio driver No mixer services exist.
crash_20180519120905_1.dmp[10880]: Uploading dump (out-of-process)
/tmp/dumps/crash_20180519120905_1.dmp
crash_20180519120905_1.dmp[10880]: Finished uploading minidump (out-of-process): success = yes
crash_20180519120905_1.dmp[10880]: response: CrashID=bp-4d1b49c9-e3f3-4d6f-a1cb-0c12c2180519
crash_20180519120905_1.dmp[10880]: file ''/tmp/dumps/crash_20180519120905_1.dmp'', upload yes: ''CrashID=bp-4d1b49c9-e3f3-4d6f-a1cb-0c12c2180519''
/home/mikhail/.local/share/Steam/steam.sh: line 927: 26147 Segmentation fault      (core dumped) $STEAM_DEBUGGER "$STEAMROOT/$STEAMEXEPATH" "$@"
ate: 60

/tmp/dumps/crash_20180519120905_1.dmp

steam backtrace

But it not 100% reproduction case because after crash occured and steam client restarted I unnable triggering crash on this page again:

Generating new string page texture 191: 1024x256, total string texture memory is 7.14 MB
[0519/151539.379439:WARNING:render_frame_host_impl.cc(2751)] OnDidStopLoading was called twice.
ExecuteSteamURL: "steam://run/359550"
GameAction [AppID 359550, ActionID 1] : LaunchApp failed with AppError_29 with ""
GameAction [AppID 359550, ActionID 1] : LaunchApp changed task to Failed with ""
[0519/151543.404324:WARNING:render_frame_host_impl.cc(2751)] OnDidStopLoading was called twice.
ExecuteSteamURL: "steam://run/359550"
GameAction [AppID 359550, ActionID 2] : LaunchApp failed with AppError_29 with ""
GameAction [AppID 359550, ActionID 2] : LaunchApp changed task to Failed with ""
[0519/151546.146958:WARNING:render_frame_host_impl.cc(2751)] OnDidStopLoading was called twice.
ExecuteSteamURL: "steam://run/359550"
GameAction [AppID 359550, ActionID 3] : LaunchApp failed with AppError_29 with ""
GameAction [AppID 359550, ActionID 3] : LaunchApp changed task to Failed with ""
[0519/151548.589380:WARNING:render_frame_host_impl.cc(2751)] OnDidStopLoading was called twice.
ExecuteSteamURL: "steam://run/359550"
GameAction [AppID 359550, ActionID 4] : LaunchApp failed with AppError_29 with ""
GameAction [AppID 359550, ActionID 4] : LaunchApp changed task to Failed with ""
Installing breakpad exception handler for appid(steam)/version(1526683293)