Is it possible to download older game updates like you can with the steam depot? Gogdb has similar manifest and build data for games, so it should be possible.

Nope! It should be hypothetically possible, but even their hoity toity client won't let you do it.

In Galaxy there is a rollback option

https://support.gog.com/hc/en-us/articles/4419630535057-The-rollback-feature-reverting-to-a-previous-version-of-the-game?product=gog

But you still cannot download the "rolled back" version, so the answer to the OP's question is still a 100% No in all ways.

...even though it shouldn't be, and GOG very much needs to offer all prior versions of all games for download, even though they don't, and even though customers have been asking for that en masse for many years.

Just for the record, what version was the game when you purchased it from GOG?

As far as I am aware, unless you tell us different, you cannot roll back to an earlier version than the one you purchased, which if you were doing the correct thing, you would have backed up and not needed any rollback facility for anyway ... only doable with Offline Installers of course, which to my mind and that of many is the sole purpose behind DRM-Free. If you have to continually rely on Galaxy, then you are not really engaging with DRM-Free.

Already mentioned by foad01
GOG Galaxy has an option to download older version for newer games

The problem is that it's limited to only 4 previous builds.

So to answer your question: yes, for any game that supports that but only for previous 4 builds through GOG Galaxy.

I admit to interpreting the portion of your post stating "if you were doing the correct thing" as the implied "you don't know what you are doing" on first read. Perhaps that was not the intent, so I will attempt a cordial answer to the version purchased question.

A search of my Orders History states June 26 2019 as date of purchase for Baldur's Gate Enhanced Edition.

I have currently two full BGEE installations on separate drives. The older install (based on date created in folder properties, June 27 2019) shows the .exe details tab in windows as product version 2.5.17.0 and date modified as 6/27/2019. The one day difference in purchase and installation indicates 2.5.17.0 would be the purchased version.

The newer install (date created listed in folder properties as June 1 2021) gives .exe details as product version 0.1.0.0 with date modified as 6/1/2021. This is the version Galaxy recognizes and identifies as version 1.3.2053.

There are many reasons why an individual might wish a particular version of a game. In this case, BGEE 1.3 has most of the improvements of the latest version, but with a very different overall UI, which I prefer. I also wanted 1.3 for certain mods which I believed at the time to only be compatible with 1.3.

Take it as you will.

edit. added .jpgs of BGEE 1.3 and 2.5.17.0 start menus.

And more bluntly, remakes, enhanced editions, and other such things have been forced upon customers with no warning or choice. Do you want Wolfenstein 3D but without the awful Spear Of Destiny addon? Too bad! Or maybe not! We can't make up our mind, the staff says!

It seems you have misinterpreted my tone and meaning, as for my part I was being completely cordial and trying to be informative.

The 'doing the correct thing' was a side comment. meant to indicate that if someone was using GOG correctly, for the DRM-Free aspect, they would never need to rollback via Galaxy, as they would have an older backup version of their own to use. Of course, many who use GOG and Galaxy in particular to install, don't care about DRM-Free.

That said, the main focus of my post was on discovering whether you could rollback to an earlier version of a game, via Galaxy, than what you bought at GOG. If you could, then of course that modifies what I said about 'the correct thing'. It would also indicate that GOG are treating Offline Installer folk as a secondary concern, which is very troubling, and certainly against what GOG stand for - DRM-Free.

Expanding on that last. When you just use Galaxy to download and install a game, getting no installer file, you are not benefiting from the major aspect of DRM-Free, which is future independence. You might be able to backup the game install folder and get it that way, but why would you bother, when you can just grab the more compact (smaller) Offline Installers, either through Galaxy or via your GOG library web page or via the third party downloaders for GOG.

In any case, while I replied to your post, I was really replying to more than just you ... the OP and any others reading it. So it was kind of general and in no way a personal attack. It was made to be informative and also get clarification, as I don't use Galaxy.

In my view, GOG should provide access to an archive of all versions of a game, since they acquired it to sell.

As others have already said, there can be a few reasons to need or desire an older version of a game. You might even want to run that game on an older PC not supported by a newer version. If GOG once had such a version, they should still have it, and I expect they do, but they just don't make those versions accessible to us, when they should if they are really serious about game preservation and DRM-Free.

GOG could repair a significant aspect of their current reputation by making older versions of games available to those that own the games at GOG. It would show they were still serious about DRM-Free and non Galaxy users.

While I am not against Galaxy or those who want to use it, it does in reality water down the support of DRM-Free.

Yes, it is possible to download older game updates from GOG using the GOGdb manifest and build data.

100% agree. As I just commented on the other thread, there are games here that need registry settings. Download via The Galaxy Way, backup the game folder, unzip that folder to a new PC (that never had the game installed properly and thus is missing the registry entries) and you can end up with a broken game. Galaxy "rollback" is no serious substitute for having a proper offline installer for future offline reinstalls on a clean OS.

Do you know this for a fact? Can you give us an example?

Because when I have tried using previous links, no longer present in my GOG library, they mostly either fail or just download the latest version.

One of the exceptions that I am aware of, is for a removed demo from your library, which happens rarely and in reality should never happen without your permission.

My guess: you're talking to a bot.