It's possible to skip the intro videos (Larian + NVidia) by placing an empty bik file in the game folder. See https://www.nexusmods.com/divinityoriginalsin2definitiveedition/mods/21
Talk:Divinity: Original Sin II - Definitive Edition
Launching the GOG copy of Divinity: Original Sin II - Definitive Edition through either the support tool ("Divinity - Original Sin 2\bin\SupportTool.exe") or the game executable directly ("Divinity - Original Sin 2\DefEd\bin"), has the game instantly close in the middle of the intro videos.
The only time it doesn't do this is if the game is launched through the GOG Galaxy client.
And if you force-skip the launcher?
That's what launching the game executable directly does.
When I last looked into this a month or two ago I attempted a whole bunch of different ways of getting the game to launch without crashing/closing without GOG Galaxy running but they were all unsuccessful. This time around I am not really interested in redoing all of that so I only did some quick 5-10 minutes of testing before undoing the undo of my original edit.
You can of course skip the included custom launcher itself by setting up a custom launch option in GOG Galaxy that launches the game executable directly, but this only skips that specific launcher -- it doesn't skip GOG Galaxy (and is in fact only usable from within GOG Galaxy).
I've also reinstalled the game using the offline GOG installers and that install, too, failed to launch properly when not going through the GOG Galaxy client.