If there are any crash dumps being created, they would be in the bin folder with the executable, named for the date and time of the crash, such as 'CrashDump - 05-29-2020 01h 23m 45s.dmp'.
Did you try both the EoCApp.exe file and SupportTool.exe in the '..\Divinity Original Sin 2\DefEd\bin' folder (or '..\Divinity Original Sin 2\Classic' for the original release)?
Try right clicking the EoCApp.exe executable, select Properties, switch to the Compatibility tab and check off the 'Override high DPI scaling behavior' option (set it to Application), maybe run as administrator and disable fullscreen optimization, and set a Win 7 or 8 compatibility mode.
You may have checked / tried some of this already, but:
If you have any generic or obscure USB controllers (or other devices) plugged in, try disconnecting them. Crashes on startup with faulting module names of ntdll.dll and EZFRD64.DLL, can (particularly for the latter) be related to USB controllers or PS2 to USB adapters (for various games).
Normally, GOG should install the redistributable packages if required with the game, but you can check, and reinstall them manually:
- Visual C++ Redist 2017 (64bit), now included with the 2019 release (if this is a problem, usually there is an error when starting from the executable, though, mentioning a VC related dll)
C:\Program Files (x86)\GalaxyClient\Dependencies\__redist
If you get an error mentioning the api-ms-win-crt-runtime-l1-1-0.dll file, it is part of the Microsoft Universal C Runtime, and on Windows 7 or Windows 8.1 can be downloaded here
, or gotten through Windows update (it is already part of Win 10).
Try browsing to the '..\Documents\Larian Studios' folder and delete the 'Divinity Original Sin 2 Definitive Edition' folder.
This folder contains the saved games, configuration files and a level cache folder. Normally I would suggest renaming the folder for troubleshooting purposes, but if you don't have any saved games that isn't an issue.
Next, extract the replacement folder from this download
into your '..\Documents\Larian Studios' folder, and see if that will let you start the game.
The graphicSettings.lsx file is set to 1280x720 Windowed mode, Very Low quality preset and low audio quality, which you can change in the options (manually, or hit autodetect) if this gets the game to start.
Try doing a clean boot and then test the game. Click Start, or hit WinKey-R, type in msconfig and hit enter; in the General tab, click Selective Startup, uncheck Load startup items (if required) and leave Load system services and Use original boot configuration options checked. Next, click on the Services tab, check the box to Hide all Microsoft services, then click the Disable All button (maybe make a note of which are currently enabled/disabled), then click OK and reboot the computer.
Run msconfig again to switch back to the normal boot configuration.
If that doesn't help, please email email@example.com with a dxdiag report (WinKey-R, type in dxdiag and hit enter, then when it finishes loading click on the 'Save All Information...' button and save the report somewhere handy). Also check the '..\Divinity Original Sin 2\DefEd\bin' folder for the gold.log file, and if there are any 'CrashDump' files being created, zip a few together to include.