How can I change the rendering to Software or DirectDraw (as opposed to Direct3D) like with the old config tool before the patch?

We removed those options and rewrote the configtool. The options you mentioned made sense seven years ago. By now, everyone has a 3D accelerated card that supports DirectX (even onboard/laptop GPU's).
We also had some trouble with those rendering methods in the past, and with new hardware out there, especially since we were trying to get the game running normally in higher resolutions. So we removed those options because they're "obsolete" and troublemakers.

Thank you for your reply! The reason for my question is simple: The Direct3D Option unfortunately doesn't work with wine emulation under Linux.
So I take the opportunity to ask, if the other rendering options are completely removed, of if there's a way to manually activate them in some way?
Thanks again.

The other options are completely removed, so there is no way to manually override the rendering system.
As DK said, there were problems with those rendering systems in the past, and these only increased over time because of discontinued support from Microsoft for DirectDraw and more OS restrictions for dabbling in software rendering. So the only viable rendering mode left is Direct3D.
Unfortunately, I have only little experience with linux, and no experience whatsoever with wine, so I'm afraid I can't help you there. I do hope you get to enjoy the game in another way, though!

Sounds great, despite the few inconsistencies. I thought something like that should make it Linux-runnable. I would love to get hold of the old configtool,so is there a way you could upload it somewhere? I suppose this wouldn't seriously violate any copyright nor count as warez, so if you'd make it available, I'd be more than happy to mark your post as the solution.
I guess it would be even better, to get the GoG staff to make it available for download. I'll ask them about it.
Edit 1: I send them a message, let's hope they'll be so nice as to include the old configtool somewhere in the download.
Edit 2: I got a reply, and they'll try to obtain the configtool and upload it. Woohoo again for the great support gog.com provides. Makes me happy.
Cheers

I actually tried pretty hard to find a simple way to publish the file anonymously on the web. That wasn't too easy I'm afraid, but I've been contacted the good GOG folks, who will post the file here. I'm on travel now, however, so it will take a day or two before I can send the file.

NIce to see how fast this got sorted out. Thanks again for your effort.

Did anyone get the file? Or was there another solution?

I have not found the file posted anywhere on GOG. Might be your best bet to contact GOG support directly, referring to this thread, and ask them if the file was posted where you can retrieve it.

Thought as much. But wanted to know if there was another solution. Thanks

I did send them the file, but they might have various reasons for not publishing it. Let me know if you need it from me.

I'd like to give it a try if possible.

If you want me to send it to you, I'll need your email address ;-)

I suppose that might help.
Thanks for sending the tool. It solve my issue. Hopefully they include a couple of options in the patch as well.