I was not going to update, but for some reason, that I don't know of, I found out that my game was updated. The point is, game was modded, I spent time into it, merging manually and testing. Not only the game had an update that does not concern me (I personally don't need the simplified chinese) but after the update the game wont even start! Even with a clean up no mod setting!
I knew that was going to happen when updating that's why I didn't want to!
And when I revert back to the good old 1.31 (A) the game, with or without mods, was not going to start either. I had no choice but to unistall it, never going to see the end because updating not only broke all the mod but also the entire game. To download all of it again and mod it like I did.. nope, too much time.. I really am mad.
Why do the dev push an update for everyone if that only contain support for language? Can't they just make it an addon for those who really need it?

GOG Galaxy is optional. So if you don't want the game to get updated on its own, you just don't need to use Galaxy to play it.

You wrote: So I don't see your point of "game-breaking bugs".

I only said, if you don't want updates to break your heavily modded game, then don't use GOG Galaxy. It is optional. You can play your games without it (offline installers). Even after installing them with Galaxy you can start them without it. Just create another shortcut to the exe file in the installation folder.

And you can download the latest version or update -if you really need it to fix game-breaking bugs - on your own as offline files too. Just use your browser or the unsupported GOG Downloader.

The point is that you don't need GOG Galaxy to keep your games up to date. That's a good question. Just don't use it and such a bug won't happen again.

I also had auto-updates enabled, but I was able to roll back to 1.31(A) easily enough.

I went to the game's Settings page (the MORE button, and Settings in the dropdown), unchecked "Automatically update to newest version", and then chose version 1.31(A) from the list that appeared.
It didn't re-download the entire game; if I recall correctly it was only a few GBs.

I have the GOTY version, but I would imagine the above also applies to the non-GOTY version.