Installed Galaxy via Lutris and through that Original Sin 2. Setup works fine (except for a bit of .Net runtime but that only appears to be for the launcher). Starting the game directly via "Divinity - Original Sin 2\DefEd\bin\EoCApp.exe" works like a charm, logo, initial loading, main menu everything as it should be.
But when I try to enter the game (either by resuming an existing story or trying to start a new one), things go south. The loading screen appears and looks normal. Music keeps playing, tips get periodically switched out but the progress bar just stays at 0.
I'm running out of ideas here. Anyone got a suggestion?

Whenever I try to search for my symptoms, I find several historical problems but the exact symptoms are different. Some Windows users seem to have similar problems, but usually when mods are involved (I'm mod-less). Tried fiddling with fullscreen settings and graphics quality and a few more arcane issues that cropped up in my searches but most/all of these seem to refer to the olden times when a threading issue prevented the initial startup (before the main menu).

Have you tried using the offline installer instead? Also, what GL driver are you using? Does Lutris install dxvk? What version of wine does it even use? I use a plain 64-bit wine-4.0.3 prefix with latest dxvk, and the game installs and works fine. I at least completed the intro chapter and a little after, but have other priorities.

Not yet. my archived backup is a couple of years and several patches out of date and it was such a huge download. Also, I did not have any skillpoints in setting up installers by hand in Wine. It does. Tried Wine lutris-5.7.5-x86_64 (the default), lutris-5.0-x86_64 and System (5.0 (Ubuntu 5.0-3ubuntu1)), although the latter wasn't up to deal with even Galaxy (some complain about rendering problems).

Most other things I try work right out of the box, even (relative) heavy hitters. Grim Dawn, Planetfall, XCom2, Tropico 6. Even cranked up to max settings (except XCom). A few other things needed a little bit of tuning and some things that aren't that important to me don't work, but at least they crash properly in some way.

I think the next step will be the offline installer in its own prefix.I had hoped someone had another idea (automatic updates and cloud saves are nice) but when you absolutely cannot find your problem description anywhere, it's usually just you.

Thanks for your time.

Well, one important fact about when it freezes for you is that it's the first time it saves, I think. So perhaps it's the cloud saves that are causing your problem. Sorry I can't really help.

Well, I just tried installing it from scratch in its own Wine bottle and lo and behold - the loading screen just works and I can at least get to character creation. Still, no clue why because the Wine settings are more or less identical. Maybe I'll give the offline installer another shot in the Galaxy bottle. I think I just copied the install over from the Windows install and trusted in Verify/Repair...

Well, it might be that Galaxy set bad permissions on save directories, although generally wine ignores permissions-related activity. I'm just shooting in the dark, here. You can safely ignore me. You're trying to operate in a mode I would never even try because I deny 'net access to all games (and wine in general), period. This means I don't get achievements, clould saves, in-game "news" and other game publisher ads, or Zacktronics games' performance histograms, but I can live with that.

edit: The fact that the load screen continues acting normally just means that the load screen is running separately from the main thread. The main thread is still hung.

Well, I got rid of the D:OS2 in the Galaxy Wine bottle and installed it again from the offline installer. Good news: Galaxy picks the game up when the install finishes, just like it should. It also works, right out of the box (except for the launcher).

So I think the moral of the story is: it's okay to try and just copy stuff over from from an existing install to save bandwidth and/or a lengthy installer. It works most of the time. But if things don't work out like this, don't forget you did that and try the proper way.

Sorry for crying wolf. Nah, as far as I can tell D:OS2 runs under DirectX11. That limits your architectural choices quite a bit. If you pull out a separate render thread (which does makes sense for a game like that), it's usually a dumb one and even something simple like switching out hint messages every few seconds would usually be done from the controlling thread. Besides, the game could still react to close events from the OS (though not completely fulfill them).
An actual stuck main event loop looks very differently and does not remain hidden from the operating system either.

Hey, BitMaster. Sorry for the necro post, but I'm going through the same issue. I was hoping you could clarify this part: Where did you install it to? Did you just skip Lutris for this step and run it with Wine directly, or did you run the installer .exe from within the Galaxy Wine environment?

Well, I've been experimenting with this today for much longer than I'd like. I got together the GOG Galaxy installer and the offline installer for the game.
I can install D:OS2 in Lutris with the offline installer. It works no problem.
I can install GOG Galaxy in Lutris and it works no problem.
Each application behaves as expected when they're in their own Wine prefixes. If I then install GOG Galaxy into the D:OS2 prefix (or vice versa), it breaks the game! Loading is stuck at 0% like before.
For some unknown reason, whenever GOG Galaxy sees the game and gets a hold of the files, I can no longer load into the story mode. Not with a saved game/profile, not with a new game/profile. I'm about to give up and either play this on Windows or just live with the fact that achievements and playtime will not be recorded on my account.
GOG really needs to address the Linux crowd and get their launcher properly ported because this is ridiculous.

One bit of info that might be interesting: When I use Norbyte's script extender, it actually reads out what modules are being loaded. When trying to load into the story mode, it hangs on "StartServer". Not sure how that factors into it, especially since my game is set to single player only.