I don't know which versions is superior to be brought to GOG. We could have the Milan and Shanghai version or the Montreal release. The Montreal is considered not the cannon versions of the game. But man, playing the Shanghai & Millan release on PC is so f@#Ked that it crashed so hard my PC always restart. That's the Steam version at least. But on the Ubisoft Connect version, that issue seemingly gone and I played it fine from start to finish and it's fine.
So if the GOG team ported the builds, I recommend they took the UC build and job's done. No hard crashes no nothing. The thing is though, I'm not touching that damn launcher. EVER!