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'.
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 (maybe sort by Date and Time) for the game - check the information under the 'General' tab below the list of events, starting with "Faulting application name..."
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) and overlays from graphics tweaking/monitoring programs or chat programs can also caused issues.
Have you tried lowering the graphics settings and resolution, or switching to Windowed or Fake Fullscreen display mode, to see if that would make a difference?
Do you have Vsync enabled, or the frame rate cap set in the options? Try enabling, lowering or disabling those options.
