Don't expect any game from big companies having their own launcher, even on steam you have to install their launcher to play their games and if they want to sell on GOG, they probably should remove the launcher so the game can be played DRM free and they wont let you play without their launcher

GOG doesn't always fix bugs in old games.

For example, when they ported over the Yakuza games, they left in the longstanding bug where items that are never supposed to enter your standard inventory slots can become placed into them anyways due to a bug, and cannot removed, and if you try to remove a bugged item then it duplicates itself and therefore wrecks additional inventory slots too.

Another example is how GOG left the GOG version of Divinity: Original Sin 1 with a game-breaking bug in it for 5 years, until the devs of that game finally bothered to fix it (and if if they didn't ever bother, then GOG wasn't going to do it themselves).

Another example is GOG's bestselling game of all-time, HOMM 3, which has bug that GOG never bothers to fix, which causes the long, unskippable Introduction video to play every time you load the game, even if you have already seen it before (even though it's only supposed to play the first time when you ever load the game, and then never again after that). Other forum members suggest useless fixes that doesn't actually fix the problem by editing the relevant registry key. But then the game just undoes the change automatically, and so that "solution" is useless.

In addition, AC: Odyssey is a quite medicore game that is full of the same exact content copy & pasted over and over again an infinite number of times. If GOG was going to try to get an AC game, then it should be the very best one, which is AC IV: Black Flag.

Anyway, that's all a moot point, because Ubisoft doesn't care to release their games on GOG anymore, and even if they did, AC: Odyssey is full of scammy microtransctions that are totally incompatible with GOG's supposed DRM-free philosophy.

But even if GOG did somehow get AC: Odyssey, then I'm sure they wouldn't fix any CTD bugs that it might have.

Pfffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffft. Considering some of the garbage GOG already has in their store...

Don't forget how several games would need a new engine to work natively in Windows again, such as but not limited to I76.