Hey,
as the title indicates: I just started the game, talked to Rabbie, got him in my party... and then cannot progress, since I cannot interact with anything. No barrel, no crate, no door, no NPC, no nothing. It's all glowing, but clicking on them does nothing. I don't know what is supposed to happen here, but this is clearly not it.

I'm playing on Win 7. Starting a new game did nothing. According to my internet search, there appear to only be two other people on this planet with that type of problem. And no resolution.

So my question is: How do I fix this? What is even supposed to be here?

...nothing at all, hm? No one ever encountered this?

I'm afraid this could be the cause of your problems with the game.
The developer dropped support for this OS about an year ago as you can read here and I suppose that the latest patches could have made the game unplayable for Windows 7 users.
If you are using GOG Galaxy, you could try rolling back to an earlier release of the game, or you could ask GOG support to provide you an offline installer of an earlier version, supposing that I am right and the latest patches are incompatible with your system.
In any case, I suggest you to contact the developer directly asking for support to solve the issue.

Hm, thanks.
I did contact the dev before, and their answer was basically a shrug. I'm obviously not going to "upgrade" my system for just one game. So I guess I may have to contact support for that offline installer of ... what version is that february 20th update?