Again, I don't think that is important as long as it is not possible at all to get the DLCs to work offline.
But since it seems to be important to you I am just installing it again while I type this to test it the way you said.

I just speak for my experience, I tried everything to get those DLCs without installing Galaxy... but in the end it was the only solution.

It's important to me that the mechanism is clear because I hate it as it is now...

A game with an offline installer that needs a connection to get DLCs seems too much DRM to me... and it's worse if you need even to install Galaxy to obtain that...

Personally I don't need a confirmation, I know how it works, already tested in every way, but if you have time and want to be sure, remove the DLC files I listed some posts above before connecting the game, else it will list them as already there.

EDIT:
Just to clarify, the DLCs does work offline, so the connection is required only once to update the DLC list.

O.K. - I just tested it the way you told me to and unfortunately I have to confirm that it is not possible to go online without the Galaxy Service activated.

But what you said here in your "edit" is of much more importance to me personally since that would mean you can actually backup the DLCs once you went online. So are you sure these are working even of you are offline? So you only need the additiona downbloaded files in your user folder?

Or to rephrase it:
If you install the game from the offline installer (without Galaxy) and add the additional files manually to the user folder does the DLC still work even though they are not listed?
The game does not list them as being there when I am offline - even though they are already downloaded.

Nice catch !! I didn't noticed that !!

But I just tried to launch the game offline, and even if it doesn't list those DLCs in the "What's new" section, I actually have the additional content in my stash ("Badland's rider outfit, Masquerade outifts, etc..."), and I can use them.

I don't have time now to check the state of the additional missions, but I suppose them are there too, I see nothing wrong in my quest log, else this thing could break a savegame...

Maybe the "What's new" list is taken from "your" profile in techlan servers, when online. (This is only a supposition, because the original game needs a user-login, while with galaxy it's not required, so maybe the profile is automatically created)

EDIT:
Anyway, a thing that I never tried, is to backup the files listed some posts above, and put them in a vanilla offline installation, to see if the game starts with the missing DLCs without even the need for a single connection.

A confirmation on this could be very useful.

clearly it's all just a mess. now the what's new section doesn't reflect unlocked content?

That is exactly what I wanted to try but I thought there was no need because of the DLCs not being shown in the list when being offline. I already backuped the additional files in the documents folder but I don't know how to access the dlc outfits inside the game (I did not play this long and only wanted to test it for others). Maybe you have a savefile for me with which I could access the dlc content?

Just look for the outfits in your stash, it's a bag near every bed you can use in the game, if the DLCs are installed you should see the related outfits there.

This is all very confusing. I wonder what made them decide to handle things this way. I mean we're talking about content that was free from the start. Why have an online requirement on some of these? But I'm wondering. IF this content could simply be dropped into the installation folder and used in-game, even without an existing connection, maybe somebody could just make those files available to those like me who can't obtain them otherwise. Again, I'm only speaking of the free, not the paid DLC packs. Hmm...

I just finished the prologue so I should be able to access all DLC content in my stash now?

At least the outfits should be already there, for weapons and quests maybe you'll need more playtime, because them are in stores or need to be activated by someone/something in the game.

I can state a thing for certain anyway, the missing DLC contents are already in the offline installer, them are just not active until the first connection, and this fact can be verified if you look at the updated files after that activation...

No sound, graphic or binary files are downloaded in the first connection, just text files with scripts.

And here a simple example of a difference between one of the original files and the updated one... you don't need to be a programmer to understand what is the "evil" command in the original one.

ORIGINAL FILE: UPDATED FILE:

I just tried it again. Installed the game with offline installer. I copied the files I archived from my previous installation (the one in the documents folder), deactivated Galaxy so the the game was not able to go online (it shows that it is offline in the main menu) and was still able to access the Badland Rider outfit in my savegame.

it's a little difficult for me to follow this conversation. if someone could summarise what has been discovered and what needs to be tested etc, i could help test

That of course would also be a possibility. I can probably try this as well - but only for the aforementioned Badlands Rider Outfit since I won't have the time to check the other stuff.

It has been discovered that the "missing" DLC files are included in the offline installer but that they are hidden as it can clearly be seen here.

I played the game normally with Galaxy enabled until I was able to access the Badlind Rider Outfit (Prologue need to be completed for those additional outfits to be accessed). I archived the files from the docuuments folder INCLUDING my savefiles deactivated Galaxy and connectivity, deleted all files and reinstalled again. Then I copied those files back into the documents folder and started with Galaxy deactivated. I was still able to accedd the Badlan Rider outfit from my save file - the outfit is shown in an extra tab.

But MAYBE the DLC was only shown in this case because I used a savefile which was created while using Galaxy/connectivity so we still need to test if a fresh install (offline installer) with only those additional files but without any savefile (start a new game) without Galaxy/connectivity is still showing the DLC after finishing the prologue.

I hope this summary is correct and understandable so far.

btw: We are doing the work GOG should have been done - we are trying to get this beast REALLY DRM-free ;)