I can't get Stellaris to run on my PC. I suspect from the GOG specific errors the game generates that this is because I am not running with Galaxy. Just curious to know if anyone else has been able to run on Windows 10 without Galaxy?

Yes, I am. Been playing it for about a month with no issues. I have never installed or used Galaxy, so that for sure puts me in your category. You might want to send a ticket to support for help with your issue, because the game should definitely run on a Win 10 machine without Galaxy. Best of luck!