I have a late-2015 iMac running MacOS Sierra.

When I try to play "Smugglers V" (base game, no DLC) I just get a blank black screen, although I can hear music in the background.

I tried contacting GOG support, they suggested redownloading the installer, switching the Wine engine and wine wrapper to the latest version, and running the winetrick ddr=gdi. After all of these were unsuccessful, GOG support told me they could not recreate the issue and basically threw their hands up in the air :(.

Support also suggested I could try installing Mono package manually
http://www.mono-project.com/docs/about-mono/supported-platforms/osx/
but after a little research I discovered that the .pkg file supplied by the mono project website does not work since 2015 (OSX 10.11 El Capitan), and I am not familiar enough with terminal to mess around manually with directories etc... for a solution which may not even work.

Support also suggesting adding "Smugger's Guild" DLC, but I'm certainly not going to purchase a DLC for a game which is currently not working, even if it would be covered by their money back guarantee.

So I am coming here in desperation to see if anyone may have another idea?...

This might be font related. I should be able to check with a Sierra iMac in the next few days.

Thanks! I'm eager to hear what you find.

It worked perfectly for me. Main menu loaded with text including the green & black tutorial message. I suspect I may know why though. The wrapper is configured to use the X11 driver instead of the Mac driver (crashes if enabled). I had installed vanilla Wine via Homebrew the other week. A prerequisite for that is XQuartz. I would guess this is why it worked normally for me.
The game did become stuck, possibly the pop-up window was behind the main window, but that's likely a game bug as it's happened to me before under Windows. After restarting everything seemed to work correctly, visited some planets, fought a battle, etc.

Thanks for your help :)!

I do have XQuartz installed on my computer (because I originally got an X11 error when I tried playing the game, before I contacted support):
https://support.apple.com/en-ca/HT201341
But installing XQuartz did not improve anything for me. That's when I contacted support, and informed them that I had installed XQuartz.

I also have Wine installed as a full app, not just the mini-version included with the game.

Is there something I need to change in the wrapper to get Wine to use XQuartz? Or do I need to install XQuartz inside the wrapper somehow?

No, it should just work. Do you still get an X11 error? The other two things I did was install it to $HOME rather than /Applications and SIP is also disabled. I wouldn't particularly expect SIP to present in this way and the engine & wrapper update should have gotten around it even if it was.
I guess I should double check which version of XQuartz is installed in case it isn't the latest. Actually, that's a thought too. XQuartz & SIP may not be getting along.

OK, I got the game to work now :)! It's rather weird how it happened though.

I first tested the Smugglers V app, and I still had the same problem (no text). I then made a copy of the "Smugglers V" app, so I would have two copies in the same directory. When I loaded the copy (which is now titled "Smugglers V 2") it worked! Then, just for the hell of it, I renamed the original Smugglers V app to a different name, and now it works too :). Then, again just for fun, I renamed the original back to the original name, and it still works.

I have no idea why changing the name would work, but it did :)!

Thanks again for all your help, it actually did help me indirectly because it got me to continue playing around with the game until I stumbled on what actually worked.

EDIT: Perhaps I spoke too soon. Now that I can see the text I have started the tutorial, but soon afterwards (when I travel to Sol to do the first mission encounter) the game freezes, returning to the opening menu but now nothing is clickable :(. I tried multiple times (including different factions and professions), but it still crashes in the same location. This is an entirely different problem I think.

EDIT2: I have contacted GOG support again, I was told to try "chmod -R 777" in Terminal with the game app, but this did not solve the crashing issue.

I'm not comfortable doing this, especially just for a game. On your suggestion, I changed the wineskin option to use XQuartz instead of WineskinX11, and now I no longer have to press command-return to see the opening menu, it just displays right away when the game loads :).

However, the tutorial still crashes in the same location. So I started a new game instead and went directly to a battle (the same way the tutorial taught me to do it), and the battle loaded without crashing :). Unfortunately however, without the tutorial I have no idea what I'm doing...

It does look like I finally have the game working properly, aside from the tutorial anyway. I guess I'll have to read the manual instead to figure the game out...