Like most folks here I'm also out of ideas to help you. My last suggestion (before you try installing on a Win7 machine) is that you try an offline install (like nightcraw1er.488 suggested) but to a mobile support (an external hard-drive or an usb pen) just to see how the game reacts.
It has happened sometimes that some users Win10 seems to prevent certain games from running because of weird protection schemes. I know it's an odd suggestion, so you can discard it if you suspect it won't change a thing.

If you have a spare, older graphics card or can loan one from someone, you could always try if the game runs with that. It makes little sense to be as drastic and install Windows 7 just for one game.

Not sure if GOG will give you a refund (since the game is not officially supported on Windows 10), but if it eases your mind at all, there's still a good chance you can play the game successfully on some other platform, like your next PC you buy etc., or even playing it in Linux with WINE etc. So in that sense your investment is not necessarily wasted even if you are unable to play it right now.

The game seems to use 3Dfx Glide (hence the GOG version uses the nGlide emulator), so I am actually quite surprised if the game has problems with some graphics cards. These Glide emulators like nGlide and dgVoodoo2 seem to generally work quite well on various different setups, so no idea why Wiz8 seems to be problematic to some setups. (Just occurred though, have you updated your graphics drivers? Just in case?)

Also since I am able to run it in Windows 10 (Pro 64bit), apparently there is nothing universal in Windows 10 that prevents the game from working. Then again, there must be some reason why GOG is not officially supporting it in Windows 10, maybe there are some Windows 10 setups where it has issues, dunno...

Yes, afraid I cannot help further. I just did (and note I do not have galaxy installed, nor ever will have):
Ran my stored offline backup setup_wizardry8_2.0.0.6.exe
Installed to c:/mygames
Ran the game.
Windows 10 pro, fully updated to latest version, with nvidia 1080ftw. No problems at all, ran really well. So I would conclude it is either:
Galaxy - I would just remove it totally
A messed up install has left artefacts, or broken libraries
Your specific hardware causing an issue
An old, or unusual windows version?
Try cleaning your machine thouroughly, a nice fresh, virtually empty system always works better than one which is clogged up with hundreds of apps and games and clients etc.

It may be a weird suggestion but you can fire up a Virtual Machine to test/play the game in the mean time.

Look if when launching the game, the process exe is running in background. If it is, close it manually and try again using some of the previous ideas to be in the safe side. Sometmes if the game process is running in background, later launchings of the game are futile.

In any way if something like this occurs (unable to launch, process running at background) keep an eye in your antivirus or firewall and make some kind of exclusion in your installed games folder or the wizardry 8 folder/exe.

I am surprised too that the 3dfx version does not work. It is emulation and it should work fine specially in modern combos. At least that is the idea/design.

Geetings

Right. I just download and installed Wizardry 8: setup_wizardry_8_2001_12_23_(22306).exe, and what do you know, it fails to work for me also!! I also note this “new” version does not have any premade characters, and there is an awful scratching noise each time it switches screens, obviously messing with the sound card.

It is therefore obvious that GOG have broken something in the later versions of Wizardry 8, which means it does not work on Windows 10 where it did before. Clearly illustrating once again why GOG need to provide a full list of all major versions and patches with those major versions, all for download with clear changelogs. The change log on this only shows file structure changes and Mac OS changes, however it is obvious that something else has been done to it.

All I can suggest for you is to try to find a copy of the 2.0.0.6 file. Perhaps in your support ticket, ask them to provide this file as that one works fine on windows 10.

I am running the 2001_12_23 version and it runs perfect under Galaxy and without Galaxy. The only chagelog in this version was an internal extructure manteinance in 2018. No files modified.

Runinng Windows 10 64 Bits up to date.

Windows 10 is spyware! How in gods name can you use this shit?

https://www.privacytools.io/operating-systems/

Well... it could be worse.
Some people even use Win10 + steam :P

Thanks for that helpful and insightful contribution to the topic in hand.

Well, at least I am aware that today the privacy under any online app or web is limited or relative. I do not have the false security feeling that a lot people like you are living with :)

At least two obstacles:

1. He would have to get a copy of Windows (7) for somewhere, to install on that virtual machine.

2. As far as I know, virtual machines don't generally work that well for games (3D graphics etc.).

I used that same installer and didn't have any issues in Windows 10 Pro 64bit.

True though it doesn't have premade characters in it, I wasn't aware older installers had that? But that has nothing to do with Windows 10 compatibility I guess.