Though the game has been buggy, I'd encountered two serious game breaking glitches. The first I was able to bypass by reloading and NOT picking up the bar before loading coal in the hopper.

The second is when Kate returns to the hospital at night. Entering the hallway from the lobby triggers a cutscene. I'm assuming that there's supposed to be a dialog option or something, but it never appears. This leaves the game stuck with NO way to advance!

I don't know if this was supposed to patched or what version is on GOG. The version listed is 1.5.07, while the 2.2 and 3.0 updates were released 7 years ago. I can't find any downloads for them on the Syberia 3 support site or Microids. Apparently they're available if you got the game from Steam...or just about anywhere else.

EDIT: I was able to continue by using a saved game I found on the Syberia 3 support site. However, I had the same issue after the ship landed at the amusement park, the game got stuck where a dialog option was supposed to appear. The game wouldn't load the save file from the support site for that point either.

I tested the game on another computer, using the same 19 GB installer downloaded from GOG. This time, I got the option for the DLC on the main menu! My save game worked just fine too, only the dialog option appeared earlier in the conversation. It's as if it's a newer version of the game...from the same download! I checked the install on both, there's no extra files anywhere and they're the exact same size. And yet...two differ versions. What the hell!?

EDIT2: I put the install from the second PC on my network and ran it on the first PC...still got the old menu and bugs. I even tried copying the save and config file to the first PC, along with the game's registry settings. EXACT same files and game config on both PCs...the first PC still loads a DIFFERENT VERSION. I have no idea what silly game Microids is playing, but it's seriously f'ed up.

I've heard of games intentionally glitching if it thinks it was pirated. The problem is I paid for a legitimate copy here on GOG and had to install the game on a second PC in a different room to get it. I ended up loading the game into Steam and using Steam Link to play it on the first PC. What worked quite well, bypassing the glitchy version stupidity. The only issue is that the mouse tracking was a little iffy, causing major headaches in some of the "interactive" parts where you have to twirl things around with the cursor.

This triggered yet another bug... When I tried to use the wrench to fix the wench on the tow truck, the game refused to recognize that it was set correctly. I couldn't figure out if I'd missed something and left the scene. When I came back, the wrench was gone and the wench was still stuck. And that was the state written to my save game, leaving me stuck yet again! The closest save game from the support site was all the way back where Kate first enters the subway. I ended up replaying that part directly on the second PC, no problems at all. ugh...

Relying solely on an auto-save system that only keeps one save file is an instantly stupid idea... And so is this multiple version nonsense. I can only hope Syberia 4 is better than this.

EDIT3: Finished the game and DLC via Steam Link without too much trouble. Finding the other building outside of the arena was a PITA though. It's hardly obvious that a gap in the fence line that opens to nothing but woods is where you'd need to go. sigh...

Well, I'd mark a reply as a solution if anyone bothered to try. I'd t reply to my own question if I had an actual solution to my original problem. Installing the game on another PC and using Steam Link is merely a workaround that doesn't actualy address the issue. I guess all I can do is just leave this here in hopes my workarounds can help someone else, though that's far more than anyone would do for me...

BTW, I got the sequel on sale from Steam,. I'd preferred buying from GOG, but if THIS is the level of support I can expect, it's rather doubtful I'll continue to make that mistake.