Check the minimum requirements, if it's equal to or above buy the game. If it doesn't run smoothly contact support. If they can't fix it ask for a refund.

I wonder the same. The system requirements on GOG and Steam are rather different and you can't be sure.

In my case the question is whether the game will work satisfactory on a low end laptop from 2011 with a i3 (sandy bridge), a dedicated Nvidia card and 4 GB of memory.

EDIT:
I bought it and can report that on the laptop above it runs, but is barely playable, not enjoyable at all. It takes about five minutes to load and everything is super sluggish, in the main menu as well as in the game. I think the game might actually need at least 4 GB of memory and is thus swapping, but I didn't investigate in detail.

Thanks for the suggestion.
The screen resolution is 1366x768, so not very high to begin with, and lowering it makes everything rather blurry. Not sure how much it helps performance wise.

I found that running the x86 version, even though it is a x86_64 machine, helps immensely since then the game requires less memory and the system doesn't swap.

EDIT:
I managed to peek at htop while running the x86_64 version and that showed 1.3 GB in swap. Given that the OS and DE take about 400 MB of memory that means a lot of game data is in swap as well, being written to and read from a really slow HDD all the time.
Given that I estimate the x86_64 version requires at least 5 GB of memory.

EDIT2:
One issue I experience is that the game crashes after a couple of minutes. I tried with the Nvidia as well as onboard Intel drivers (I think, unless I did something wrong). Is this a known issue?

Please do. On that 4 GB machine with 64 bit OS I had the 32 bit version and Nvidia graphics (set to max performance) I had it run for about 1 1/2 hours. Memory looked good (more than 1 GB to spare I think) when I checked after half an hour or so, but after those 1 1/2 hours the game reported it couldn't save because it ran out of memory. At that point it had already swapped a few hundred MB.
It's all a bit weird. After starting the game, in the main menu, the game requires more memory than actually in the game (freshly started or small park with five or so rides).

One thing that apparently increases memory consumption is saving. One save -> +100 MB of memory in use.

OK, thanks.
This is on Ubuntu 18.10 64 bit. But 32 bit parkitect since the 64 bit version starts to swap on load already.
Any suggestions on how to narrow it down a bit?
Which information do you need?

I have created a (slightly redacted) system report that I can send you, but I don't know how to pm here.

I also have two Player.log files from crashes. Seems to be due to failed memory allocations.

On a sidenote, on my Desktop machine (64 bit Arch Linux, 16 GB RAM), the game (64 bit version) sits at 1.5 GB reserved memory at the main menu and 2 GB of reserved memory after loading Maple Meadows. It is increasing, but only very slowly ( a few MB per hour).

The attached screenshot is taken from my desktop system (Arch Linux x86_64). As you can see I have Maple Meadows loaded and Parkitect takes up more than 5 GB of residential memory. I arrived there through repeatedly loading various parks. Loading a new park doesn't always increase memory usage, I'd say it's a coin flip. I haven't found a pattern to it.
This to me clearly indicates memory management issues.

EDIT: Sorry, the GOG Forum is so horrible I had to use low quality JPG to get below 500 kB to actually post here (despite it saying that the limit is 2 MB). Not that it actually threw an error when the file was above 2 MB, it just didn't upload.

EDIT2:
I gave it a shot with a second laptop with very similar specs to the one described earlier, it has just the IGP and 8 GB of RAM and running Arch Linux x86_64. The game doesn't crash due to lack of memory (in normal operation) but it drains so much power that it drains the battery even though it's connected to the power socket with a 90 W power brick (not the default 60 W). It crashed eventually, either because the power drain got too large or because it overheated.
Have you considered selling this program as a stress test?