Are you shutting down all non-essential programs (especially anti-virus) before starting the game? Firewalls can cause conflicts (generally on startup or loading screens, though) and overlays from graphics tweaking/monitoring programs or chat programs can also caused issues.
Try exiting out of the Steam client, and starting the game directly from the '..\SteamApps\common\Divinity Original Sin 2\DefEd\bin\EoCApp.exe' program file, by right clicking and running as administrator.
Try verifying local files: in the Steam library, right click on the game and select Properties, switch to the Local Files tab and then click on the 'Verify Integrity of Game Cache...' button.
With the GOG version, in the (optional) Galaxy client, select Divinity: Original Sin 2 in the left column, then click on the More button, and in the Manage menu select 'Verify / Repair'.
Try lowering the graphics settings and resolution, and switching to Windowed or Fake Fullscreen display mode, to see if that will make a difference.
If you check the Event Viewer, does that give an error code or 'Faulting Module' file name that might help identify the cause of the crash?
- click Start (or WinKey-R), then type "event viewer" into the search box. in Windows 10, 'event' should bring up 'View event logs'.
- after starting the Event Viewer, expand 'Windows Logs' in the left column and select 'Application'
- in the center column, look for a recent error for the game (maybe sort by Date and Time, or search for 'EoCApp')
- check the information under the 'General' tab below the list of events, starting with "Faulting application name..."
If that doesn't help, please email supportdos2@larian.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 zip a few of the 'CrashDump' files together to include.
