Telemetry shouldn't exist without the user's consent. Some people are not bothered by it, while others are seeing it as malware. Meaningfully or not, Unity's telemetry does write a bunch of small files every time the game is launched and closed, loses and regains focus, and other stuff. You can easily end up with a few hundred files in a several hours gaming session. Sure, it won't write massively on your drive, but it all adds up, and are more and more Unity games every day. Most indie games are now made in Unity, and unfortunately this poorly optimized engine will spread like a cancer in the future years.

I did a few tests with Train Valley, which is made in Unity 2018 version. You start the game, it writes 8 files. Close the game, another 4 files. Switch to other application/minimize it/loses focus, another 8 files. Return to the game, again 4 files. Play the game, it writes 4 or 8 files at some time intervals. Maybe with internet access it will write even more? I don't know. I have them all blocked in the firewall. These are all small files, but even a few bits file requires a full cluster write. So that's just a useless write-erase cycle in the life of a NAND memory cell.

Unfortunately this is also case of The Witcher 3, so I have doubts, that they will fix it…

I wrote some requests to support with this and they always reply, that I have bad firewall...

My games PC never is connected to the internet (i copy/paste the GOG offline installers from my Linux machine that IS connected to the internet, then install them on the Windows gaming machine).

I have never had a problem launching any of the GOG games i own (yet). So it might seem you can simply not be connected when you play and that galaxy.dll will not be a problem?

there is a problem. In order to make all these cheevos work, game itself should be aware about existence of galaxy.dll and know how to communicate to it. And if it wont be there - game will end up confused and may (depending on how game handle such errors) become unstable or even crash. Thats why in most of the cases its hardcoded dependency which you cant just throw away

Sorry, with "game.exe" I just meant the installer, not the actual game.
These would be the files you download from Gog.

And why would offline installers need to worry about achievements? Or cloud saves? If your going to use galaxy, use the galaxy downloader. Mind you same thing goes with all of it, if you want a client, online stuff, don’t care about offline installers, use steam, bigger library, cheaper etc. Good to see every store looking exactly the same, that’s what choice is for.

I dislike telemetry as well, and I dislike Unity games even more (for various reasons - slow response of controls or clunky UI which cripple any game). So I just stopped to buy games made with Unity. Last game I forced myself to play was Pillars of Eternity, that was so awful in terms of controls, UI, not to mention dull story. What you would expect from less famous studios when they use Unity engine?
just stop buying Unity games and it will cover telemetry issue :)

There are real good games made with Unity. Ori and the blind forest comes to mind.
With all the stuff going on, may eventually put a off line computer toghether to play the sequel.
Wasn't Cuphead made with Unity as well?

Or I wasn’t that great, spent most of my time trying to get the bleeding thing working correctly as it lagged every few seconds, apparently a common complaint. Gave up at the thorns in the tree in frustration too.

maybe that's an exception from rule, some games can be of good quality but most of the time it's frustrating experience. maybe it's just me, I still enjoy old games from late 90s or early 2000s and these games show how much work and dedication developers had to put into their game, even having limited technology they were able to deliver hits we still enjoy.
What is Unity and why everyone from asset flippers to giants like Obsidian uses this lame engine? in the old times developers wrote game engine from scratch, tailored it to game actual features and it resulted in unique experience, everything was snappy and lightweight. Now developers decided that we absolutely have to see zillions of games every year, everyone has to create a game (even if they have no idea what kind of game do they want or how to code basic features, leave alone bug fixing or optimization). Unity comes to save these unskilled developers from creating their game by hand. And it shows.
Stardew Valley, Book of Demons are serious examples of small studios (or one man) who were able to create great games without Unity. I always check which engine game in question uses before buying it. if it's self made engine that's a determining factor in my purchase priorities.
If you want to keep playing good unique games stop supporting Unity, if things won't change it will kill the whole scene and we'll have nothing new to play in 5 years.

its not about offline installers, but developers... While cloud saves indeed can work without additional work from their side, you cant enable and disable achievements support "on fly" (well, you actually can, but it will double the amount of work. You will basically need to maintain two versions of the same game for same store. Nobody would like to do that)

And that’s really the issue. Effectively all the installers are the same other than some galaxy UI bits. Therefore we are all using galaxy now to a lesser or greater degree. Not just new games either, there is resource being put into modifying old games from decades ago as seen in dungeon keeper, I.e. actively adding galaxy components to games that didn’t have it before. We are only marginally better off than the previous major galaxy announcement.

that's redundant. I just played good old Dungeon Keeper 2 on Origin launcher and it worked great on Widows 7. So I can safely assume this game has been updated by EA themselves, not by gog. Gog only publishes what EA gives them (DRM-free versions of their old games) and EA sells same games (with Origin DRM) in their store so they have to upkeep these games in working condition.

Dungeon Keeper 1 is a DOS game so it does not matter galaxy or not - it will work on ANY OS granted it has dosbox installed, Dungeon Keeper 2 is early Windows game and that's more tricky to maintain.

Dungeon keeper has been updated only to add galaxy features, it is clearly stated in the change log.

Internal Update (21 March 2019)
[WINDOWS] added cloud saves functionality

You can find more about this topic here:
https://www.gog.com/forum/general/gog_galaxy_required_in_certain_games

This is nothing (for once) that EA have done.