Apparently there is a way to fix the DLCs issue until GOG will finally get around to it: https://www.gog.com/forum/dragon_age_origins_ultimate_edition/where_are_all_the_dlcs_1/post10

Will take a look and try it out later.
Thank you!

Try to ask support, they probaly will update the game or rollback to the previous version untill they finally hit the spot.

Intel seems to want to replace HT with more E-cores, but that just creates a new problem whereby hard locking games to specific threads might accidentally lock it to a (slow) E core designed for background tasks instead of a (fast) P main core. The new heterogenous CPU's can range from 2C/2T (P) + 8E mobile chips through to 8C/16T (P) + 16E and the first E core could start anywhere from Thread 3 to Thread 17, which is exactly why sane stores don't try and hard-code one number for everyone. There's really no need for any of this though. The main thing that stopped the crashes was applying the LAA / 4GB RAM patch. Once that was applied I found the game works fine. It's not like we weren't happily playing the game on 4C/8T chips (eg, i7-2600K Sandy Bridge's) over a decade ago.

Screenshot (in Process Explorer) of DAO (older GOG version) with LAA / 4GB RAM patch applied but not the dual-core restriction. The bottom numbers 1,012,080 and 1,545,124 refer to the Peak Working Set & Peak Private Bytes of memory (1.0GB and 1.55GB) used, so the 4GB fix is certainly a good idea. Beyond that, as you can see, the game happily spreads its threaded load across 6C/12T, 8C/16T, etc, CPU's very well.

I don't blame you. Constantly deleting good working versions of offline installers and gating access to the "rollbacks" behind a client is about as far removed from "game preservation" as you can get. Personally I learned my lesson with Divinity Original Sin where it took 5-6 years to replace the bugged language update with a bug-free version, and all that time people filing support tickets were met with "Just Use Galaxy" gaslighting instead of putting the older installer back. Sheer luck I kept the older version on a secondary backup. Since then, I don't delete any "known working good" backed up versions, nor even rush to download new patches for the sake of chasing a number unless there's actually something that justifies it (eg, a major bug-fix by the developer).

Edit: Yes the DLC are stores in Addins.xml file mentioned above rather than the registry, but you may still need the registry entries anyway (eg, if you zipped up the Galaxy installed game folder, then unzipped it on a new PC that's never had DAO installed), you may find it won't start. Various other games here, eg, Oblivion & Fallout 3 similarly won't start without theirs if all you do is copy the game folder minus the relevant registry keys.

This worked. Thank you!
The DLCs show up now after I downloaded Dragon Age Origins - Ultimate Edition build 2 through lgogdownloader:

This is what I did:

Downloaded build 2 through lgogdownloader using Galaxy install/API: Placed the AddIns.xml downloaded from s1lver1us' post in /Documents/BioWare/Dragon Age/Settings/

Started the game through its bin folder .exe, as I normally do to skip launchers (because I tend to personalize game settings through the .ini files, if any.).

And it worked.

Thanks for sharing your situation. Yes, lesson learned.

Steps above made the game recognize the DLCs.
I don't think my Windows 10 boot has any registry entries for DAO because before using the filled AddIns.xml file the game had no DLCs present.

Game opened fine. I tried starting new games for both the Expasion (Awakening) and main game and they both seemed to work. Also tried starting campaings through DAO main menu campaings menu and the ones I tried seemed to also work.
So, thankfully, DAO seems to not use any registry entries to confirm the presence of DLCs?

GOG support wrote that they know the problem and are already solving it.

Especially when it's something you easily can do on your own, when it really is necessary. And core affinity better should be handled by the system, not an app itself.

Yet they still continue to repeat the mantra of Galaxy being optional, even when their own support tells you the opposite. And it's not the only functionality on GOG which is restricted to Galaxy.

What I especially hate is the large number of in-place updates with such risky changes (which easily overwrites your old installer when you don't take care). They do have a build system with build numbers now, so why not incrementing the build number with every update instead of deploying different installers with the same version number? Even worse, they deployed changed installers for games where the changelog contains nothing than "Verified xyz" lines and documents no changes at all. So why a changed installer when only the functionality has been verified, GOG?

Try just using start without cmd, like:

start /affinity FF "C:\GOG Games\Dragon Age Origins\bin_ship\DAOrigins.exe"

(see this StackOverflow article for more examples.

Another option is to use ImageCfg to modify the DAOrigins.exe (or any other .exe file) to use the cores you select (the -a 0xff parameter should make it use up to 8 cores - unsure if you can use 0xffff to stretch up to 16).

DAO does not need any registry entries at all. Everything (DLC, Settings, Mods, etc) are all either stored in the main game folder or in your BioWare\Dragon Age Origins Documents folder.

The only registry entry that can make a difference is

[HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\BioWare\Dragon Age]

and thats only used by the Configuration Utility to read where the game is. (The Config Utility will still work fine without it.)

I should add that I have the game installed at the moment with no registry entries at all for it and it all works fine including the utility.

Edit:

Though I did downgrade the game to the version before they added cloud saves as like others here GOG's new version was having slow downs, downgrading it fixed it.

bin_ship/DAOrigins.exe has ProcessAffinityMask set to 3 in load configuration section of the exe
To fix the affinity issue change ProcessAffinityMask to 0 in the exe

Get PE-bear
Open "bin_ship/DAOrigins.exe" in PE-bear
Go to "LoadConfig" tab and change ProcessAffinityMask to 0
Right click on DAOrigins.exe on the left side view and select "Save the executable as..." and overwrite the original exe Alternative method with hex editor
Open "bin_ship/DAOrigins.exe" in hex editor
Go to offset 75a130 (offset was determined using PE-bear)
Change "03 00 00 00" into "00 00 00 00" and save changes

With these news updates i am going to keep the old backups and not download the new files until gog says they fix the problem you mentioned.

Or, and hear me out for a sec, gog could've just left things alone and not break the offline installers for games that were working just fine, and left any non-critical fixes to the user. Instead, we now have an extra step we didn't need before, because someone at gog read pcgamingwiki fix notes for the game, and thought all those should be applied without carefully considering how it might break the game for some.

Crazy idea, I know.

First things first: if they were going to make the affinity change they should almost certainly have set it to use 4 cores instead. A 2.4Ghz Core2quad is the recommended spec after all, and that had 4 cores hence the name. So the game was definitely designed/ tested in 2009 for stability with 4 cores. There's no reason to set it to two under those circumstances.

Having said that, two cores ought to be enough; even if running on e cores. Which they shouldn't be given every Intel chip with e cores has at least 2 p cores too (all AMD chips are 'p' core only to this point for anyone wondering), though see below.

Core2 is 15 years old and was not a high frequency chip. While Intel had 5 years of literally no IPC improvement recently even e cores have Haswell level IPC, which was two big architectural and two moderate ones better than Core2. That's way above min spec, and if not better than recommended would have to be close.

In theory certainly, but practically Windows' (system/ process) Scheduler has had and still does have some fairly notorious issues even if/ when left to its own devices.

The issues with new chips have been talked about most- and perhaps relevantly, since one definite recent problem was Scheduler assigning performance tasks to e cores when it wasn't meant to. But it has issues with old software too, and while fixing the new problems may be fairly slow fixing the old ones basically never happens.

Galaxy install files are the org untouched format files. The Offline D/L Game files are inside a wrapper program (For Ads) and in bin format.

I always download every updated version of the game files, plus every update patch files. Keep a 4 TB HDD just for those files, incase a need to install offline or revert to a previous version.