Launching Pinball FX3 fails with an immediate crash (no window is show, just a bit of activity logged to STDOUT:

GameAction [AppID 442120, ActionID 1] : LaunchApp changed task to ProcessingInstallScript with ""
Installing breakpad exception handler for appid(steam)/version(1535062307)
GameAction [AppID 442120, ActionID 1] : LaunchApp changed task to SynchronizingCloud with ""
GameAction [AppID 442120, ActionID 1] : LaunchApp changed task to SiteLicenseSeatCheckout with ""
GameAction [AppID 442120, ActionID 1] : LaunchApp changed task to CreatingProcess with ""
GameAction [AppID 442120, ActionID 1] : LaunchApp waiting for user response to CreatingProcess ""
GameAction [AppID 442120, ActionID 1] : LaunchApp continues with user response "CreatingProcess"
Opted-in Controller Mask: 70
Game update: AppID 442120 "", ProcID 21869, IP 0.0.0.0:0
>>> Adding process 21869 for game ID 442120
GameAction [AppID 442120, ActionID 1] : LaunchApp changed task to WaitingGameWindow with ""
ERROR: ld.so: object '$STEAMBASE/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
ERROR: ld.so: object '$STEAMBASE/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
ERROR: ld.so: object '$STEAMBASE/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
GameAction [AppID 442120, ActionID 1] : LaunchApp changed task to Completed with ""
ERROR: ld.so: object '$STEAMBASE/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
ERROR: ld.so: object '$STEAMBASE/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
>>> Adding process 21870 for game ID 442120
>>> Adding process 21871 for game ID 442120
ERROR: ld.so: object '$STEAMBASE/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
ERROR: ld.so: object '$STEAMBASE/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
>>> Adding process 21872 for game ID 442120
>>> Adding process 21873 for game ID 442120
ERROR: ld.so: object '$STEAMBASE/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
>>> Adding process 21874 for game ID 442120
>>> Adding process 21877 for game ID 442120
ERROR: ld.so: object '$STEAMBASE/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
ERROR: ld.so: object '$STEAMBASE/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
>>> Adding process 21879 for game ID 442120
ERROR: ld.so: object '$STEAMBASE/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
ERROR: ld.so: object '$STEAMBASE/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
>>> Adding process 21882 for game ID 442120
>>> Adding process 21893 for game ID 442120
>>> Adding process 21898 for game ID 442120
ERROR: ld.so: object '$STEAMBASE/ubuntu12_64/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS64): ignored.
ERROR: ld.so: object '$STEAMBASE/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
>>> Adding process 21907 for game ID 442120
Game update: AppID 442120 "", ProcID 21873, IP 0.0.0.0:0
WARNING: radv is not a conformant vulkan implementation, testing use only.
Game update: AppID 442120 "", ProcID 21873, IP 0.0.0.0:0
CAppInfoCacheReadFromDiskThread took 1 milliseconds to initialize
registry.cpp (250) : Assertion Failed: on disk registry has changed and is marked dirty - we're about to lose data.
registry.cpp (250) : Assertion Failed: on disk registry has changed and is marked dirty - we're about to lose data.
Installing breakpad exception handler for appid(steam)/version(1535062307)
CApplicationManagerPopulateThread took 33 milliseconds to initialize (will have waited on CAppInfoCacheReadFromDiskThread)
gameserver.cpp (684) : Assertion Failed: usGamePort != usQueryPort
gameserver.cpp (684) : Assertion Failed: usGamePort != usQueryPort
ERROR: ld.so: object '$STEAMBASE/ubuntu12_64/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS64): ignored.
assert_20180901101815_11.dmp[21926]: Uploading dump (out-of-process)
/tmp/dumps/assert_20180901101815_11.dmp
assert_20180901101815_67.dmp[21928]: Uploading dump (out-of-process)
/tmp/dumps/assert_20180901101815_67.dmp
>>> Adding process 21925 for game ID 442120
Game removed: AppID 442120 "", ProcID 21873 
No cached sticky mapping in ActivateActionSet.pid 21875 != 21874, skipping destruction (fork without exec?)
assert_20180901101815_11.dmp[21926]: Finished uploading minidump (out-of-process): success = yes
assert_20180901101815_11.dmp[21926]: response: Discarded=1
assert_20180901101815_11.dmp[21926]: file ''/tmp/dumps/assert_20180901101815_11.dmp'', upload yes: ''Discarded=1''
pid 21926 != 21925, skipping destruction (fork without exec?)
assert_20180901101815_67.dmp[21928]: Finished uploading minidump (out-of-process): success = yes
assert_20180901101815_67.dmp[21928]: response: CrashID=bp-a3b315b1-1ace-4c46-b62d-f2a382180901
assert_20180901101815_67.dmp[21928]: file ''/tmp/dumps/assert_20180901101815_67.dmp'', upload yes: ''CrashID=bp-a3b315b1-1ace-4c46-b62d-f2a382180901''

You should find the MiniDump file for that in your database (ID: bp-a3b315b1-1ace-4c46-b62d-f2a382180901).

Using the Proton Beta 3.7-5 doesn't help either.