I just downloaded the game and installed the game for my Ubuntu 18.04.2 system. When I tried to start it the game did not even launch. When I tried starting the game via the terminal I got this error message:
~/GOG Games/Imperator Rome$ ./start.sh
Running Imperator: Rome
./Paradox Launcher: error while loading shared libraries: libgconf-2.so.4: cannot open shared object file: No such file or directory

I just checked the requirements on the website and I didn't see any dependencies that had to be installed to get the game to launch.

Will I just need to install the libgconf-2.so.4 library myself to get the game to run?

I really dislike that most of the linux versions of the games do not list out what dependencies are required for the game to run. I've experienced a lot of times when the linux version does not work and everyone has to figure out a fix or workaround.

I don't have the game but I thought that I'll check the forums first if anyone is having serious issues getting the game to start before I buy.

If you type "locate libgconf-2.so.4" , do you get any results?
Mine shows that it's located in /usr/lib/x86_64-linux-gnu/

If you don't have any results, it means you need to install the library. I think it's "libgconf-2-4".
Description here: https://projects-old.gnome.org/gconf/
I would have thought that it would have already been installed if you're using the gnome desktop.

Game crashes right after pressing 'Play' ('Spielen') in the launch screen. This is with libgconf dependencies solved.
Running Nvidia drivers on Ubuntu 18.04.2/Gnome shell.

From the logs:
JS ERROR: Exception in callback for signal: set-cursor-location: TypeError: this._currentWindow is null

(node:7936) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 finish listeners added. Use emitter.setMaxListeners() to increase limit

BTW getting a warning concerning dlc, too:
[DlcService]: dlc_signature NOT valid, DLC will not be loaded

I just tried switching to Intel graphics in an attempt to confirm that it's an issue with Nvidia graphics. Still crashed on startup. I've also tried running the Imperator binary directly in the terminal using both Intel and Nvidia graphics. No luck.

I ended up buying the game.

Using a 980M on a laptop. Game crashes to desktop on full screen.

Setting the game to run on windowed mode, I can't change the window size on the launcher settings. It's just stuck at native resolution (1920 x 1080).

If I just run it in windowed mode, I get the loading art screen, then the game crashes.

The game dumps and logs the crash under ~/.local/share/Paradox Interactive/Imperator/crashes

I don't have the time to go through the logs. But here's an excerpt inside exception.txt as an example:
/lib/x86_64-linux-gnu/libgcc_s.so.1(_Unwind_RaiseException+0x14b) [0x7f060a53d22b]
./imperator(__cxa_throw+0x63) [0x217aad3]

I guess I'd better submit the crash reports to Paradox or something.

For now I'll be playing the game in Windows. :(

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EDIT UPDATE:

I ran gdb on the imperator binary.

Threw up a segmentation fault:

Thread 18 "pdx_mp_update" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffabfff700 (LWP 5589)]
0x00007ffff72db7db in get_adjusted_ptr(std::type_info const*, std::type_info const*, void**) ()
from /home/********/GOG Games/Imperator Rome/game/binaries/libpops_api.so

libpops seems to be a proprietary library, which is included in the game install. I don't know what it does.

I'm having the exact same issue. Looking at the dependencies of libpops_api.so (e.g. libresolv, which is used for DNS) along with the name of the function that causes the segfault makes me think it has something to do with multiplayer support.

Of the other Paradox titles I have installed, both CK2 and Stellaris also include versions of this library, and both of them run fine on my system. Unfortunately, my copies of both of those games are 32-bit, whereas the build of Imperator in the GOG package is 64-bit, so I can't test it with the other games' libpops_api.so.

I did try preloading different versions of libpops_api.so's dependencies, but to no avail.

Can you launch the game if you disable your network interface from Network Manager before starting the launcher?

I can confirm that disabling my network interface allows the game to launch.

Interesting. I have a thread open at https://forum.paradoxplaza.com/forum/index.php?threads/i-r-linux-game-usually-fails-to-load-from-launcher-when-using-nvidia-418-drivers.1171095/ if you want to lend your support. I think you need to register your game with paradox to access that forum, though, so don't worry if you'd rather not.

I did reinstall the game with their latest installer (1.0 something sulla) because it was a different version then the launch version, I think. After I installed the missing library manually the game did start. But I am not running on the 418 nvidia drivers but on the "new" 430 drivers. The game worked fine for me. But I just played for one hour or so. So I doubt that this is anything to go by.

Installed the latest version 'imperator_rome_1_0_0_sulla_29073.sh', however the game still crashes ofter pressing 'play' in the Paradox launcher and when launching the binary directly.
However, the game launches without issues after having deactivated the network interface. I was a few minutes into the Tutorial and was able to go on playing after having reestablished the internet connection. So the problem seems to be with network connectivity at start up of I:R.
Nvidia drivers are on version 390 btw.

Greetings to everyone.

This is just to confirm that disabling network fixed the game launch issue.

I am on Debian Testing 64 bits, AMD graphics.

you need gconf2 package.
sudo apt install gconf2

Same -- launching with `unshare -n` to disable network allowed it to launch.