thanks again for the help:

installing the i386 libraries did not help, reinstalling steam and then reinstalling Pillars did not help.

gdb output leaves me baffled but does not say a lot (first time I used gdb)
Reading symbols from ./PillarsOfEternity...(no debugging symbols found)...done.
(gdb) run
Starting program: /media/games/SteamLibrary/steamapps/common/Pillars of Eternity/PillarsOfEternity 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Found path: /media/games/SteamLibrary/steamapps/common/Pillars of Eternity/PillarsOfEternity
Mono path[0] = '/media/games/SteamLibrary/steamapps/common/Pillars of Eternity/PillarsOfEternity_Data/Managed'
Mono path[1] = '/media/games/SteamLibrary/steamapps/common/Pillars of Eternity/PillarsOfEternity_Data/Mono'
Mono config path = '/media/games/SteamLibrary/steamapps/common/Pillars of Eternity/PillarsOfEternity_Data/Mono/etc'
[New Thread 0x7ffff7fde700 (LWP 12275)]
[New Thread 0x7ffff4049700 (LWP 12276)]
[Thread 0x7ffff4049700 (LWP 12276) exited]
[Thread 0x7ffff7fde700 (LWP 12275) exited]
[Inferior 1 (process 12270) exited normally]
(gdb) 

At least on my system it's a 64bit binary, so I would be surprised if installing 32bit libs would do much ^_^

[Inferior 1 (process 12270) exited normally] it doesn't seem to be crashing at least, it just exits without any reason?

Did you check the Unity log as suggested by others previously in the thread?

Apologies for the delay in coming back...
* I checked .config/unity3d/ there is no Obsidian... or Pillars... folders at all
* I did find that the Player.log updates everytime I try to start Pillars and says
[code]Player is already running
(Filename: Line: 439)/code]

A quick google indicated that could be related to having a chrome window open or chrome process but even rebooting and manually ensuring all chrome processes are killed still produces this bug - I am wondering if this is an old unity version that "thinks Gnome is running a unity process" or something ?

now downgraded nvidia driver to version 390.87 and it works -- so < the version of unity3d shipped with > PoE does not work with 396.54 ... ok lets see if once up and running I can get it to restart after driver update (doubt it) thanks for all the help

It looks like Unity is quite broken when it comes to making sure only a single instance of the game is running. There's some analysis here:
https://forums.obsidian.net/topic/84736-game-dosent-start-using-the-steam-client-linux/
https://steamcommunity.com/app/240760/discussions/1/617320628324498086/

The bug was fixed, but each game affected needs to be updated. I'm not sure what version of Unity PoE uses.
https://forum.unity.com/threads/bug-in-unity-when-running-chrome-on-linux.441253/

I guess not only Chrome but any program that uses the same way to spawn child processes will trigger the bug.

TLDR, at some point Unity ends up comparing the command lines for running prcesses with the string "/proc/self/exe" and not what readlink("/proc/self/exe"... points to. The lesson here is for parents not to name their children /proc/self/exe. Looking at you Chrome!

Here's very quick python script to find any process on the system that might be a problem:
import os

procdir = "/proc"
for proc in os.listdir(procdir):
    try:
        with open(os.path.join(procdir, proc, "cmdline"), "rt") as fd:
            cmdline = fd.read()
            if "/proc/self/exe" in cmdline:
                print(proc, cmdline)
    except Exception:
        pass
(Considering Skitt's Law and that I'm criticizing Unity here, the code above probably will not work!)

Finally figured it out!

It was the VPN connector application (PIA) that was causing Unity to think that it was already running...

also works with nvidia 396.54 again

very odd but perhaps for future reference...

Might be worth letting them know, I guess?

Also, PIA has OpenVPN profiles, which should work through straight-up Network Manager without any additional software (once you get openvpn installed, as it's possibly not).