They transcoded the videofiles from "Indeo 4.1" to "Motion JPEG" and added some DirectX wrapper as well as DirectX 9 to the installer.
Look at the screenshots for further details. I picked the Intro video as example.
They've also added support for Galaxy Overlay.

That's the German manual. It wasn't removed today. It was removed on January 31 (https://www.gog.com/forum/general/the_what_did_just_update_thread/post23345).

I've just did a lib update, probably that's why I noticed today.

The number of games in my library just decreased by one, but I have no idea what's missing or has been merged with another title.

Cultist Simulator:

Apparently the offline installer went from Patch 2019.9.a.1 to Patch 2019.9.b.1

Chengelog info is still from October 2019

Heroes of Hammerwatch

Update to V104.

No changelog.

The Suicide of Rachel Foster

Updated to 1.0.3D (Galaxy & Offline Installer)

Not so real changelog from Steam. ;)

Patch notes from steam V104

Mercenaries now start with the squire pet selected
Fixed issue with deleting mercenaries from ledger
Arena now always gives 5 swords when beating it with a mercenary
Beating a dungeon in a multiplayer game while dead now revives mercenaries instead of incorrectly marking them as dead
Walking pet now moves a bit better and can now teleport to the player in some cases
Waning and Waxing Crescent can now be found in all dungeons, still requires completion of Moon Temple
Papers of Nobility are now attunable
Fixed some mistakenly placed destroyable secret wall parts
Fixed a spelling error
Fixed a glass walk not spawning correctly



We're aware that there have been issues with multiplayer lately that are affecting a lot of people, sorry for the frustrations, we don't have answers just yet, but it's being looked into with our multiplayer service provider.
Apologies for the troubles everyone has been having, hopefully we can update everyone soon with a solution.

Kenshi

Update 1.0.45c (28 February 2020)
BUGFIXES:

Fixed a file mix-up with the Korean translation, it should be much more accurate now.

Update 1.0.45b (28 February 2020)
BUGFIXES:

Fixed dialogue interrupts not working on announcements when another NPC interjected. Could affect certain player base raids.
Fixed crash dismantling cages with an unconscious occupant.
Kidnapped pack beasts from wandering traders will no longer have their inventory automatically re-stocked.
Fixed possible crash when dismantling a turret that is being used (which should be impossible)
FCS/MODDING
Fixed crash if modded character mesh has UVs outside 0-1 range (other than head)
Fixed an issue with CHARACTER "stealth stats" property
Fixed crash if character model failed to load due to missing skeleton file

Low Magic Age

Low Magic Age has been updated to Version: 0.91.23.3 (Offline installers not yet updated)

No changelog

Apparently the game that was removed was STASIS. It just showed up in my library and was marked as new, and the total number of games in my library is now the correct number again.

Strange glitch.
I had no problems with my copy of 'Stasis'. =)

Perhaps it has something to do with the fact that a Kickstarter backer of BEAUTIFUL DESOLATION gave me a gift code for the game, and I redeemed it on February 26. I've never seen a gift code like it. In my orders history, it doesn't show who gifted it, so it looks like it does when I click a banner on the main store page to claim a freebie. If you bought that game during its launch promotion, you got STASIS for free. I didn't have STASIS in my account when I redeemed the key for BEAUTIFUL DESOLATION. STASIS was added as soon as I redeemed the key, but apparently GOG staff removed it yesterday and re-added it about 8 hours ago. I'm not sure why they'd do that, but everything seems to be fine now. Perhaps they wanted to give STASIS its own order number. I don't remember it being listed in my orders history when it was first added to my account, but now it is.

AI War 2 Standalone installers updated 04 & 05 March 2020:
- Game:
--> Windows: 2.006 ⇒ 2.007;
--> Linux & Mac: 2.002a ⇒ 2.006 ⇒ 2.007.
- DLC:
--> Windows: 2.006 ⇒ 2.007;
--> Linux: 1.9 ⇒ 2.006 ⇒ 2.007;
--> Mac: 2.002a ⇒ 2.006 ⇒ 2.007.

***

Godhood [InDev] Standalone installers updated (0.16.2 ⇒ 0.16.9): 05 March 2020.

***

Noita [InDev] Standalone installer updated (20200224-1627 ⇒ 20200303-1535): 04 March 2020.

(For anyone interested, previous changelogs (which weren't available until now), going as back as the game's initial InDev release, can be found here).

***

OUTBUDDIES Standalone installer updated: 1.53b ⇒ 1.54.

***

Through the Darkest of Times Standalone installers updated (1.01.3 ⇒ 1.03.6): 04 & 05 March 2020.

***

Vambrace: Cold Soul Standalone installers updated (1.09 ⇒ 1.10): 04 March 2020.

***

Standalone installers updated 04-05 March 2020 with no changelog:
- The Blind Prophet: 1.16 ⇒ 1.17.
- The Colonists: 1.4.1.1 ⇒ 1.4.1.2.
- Crossroads Inn, and its DLC:
--> Game - Mac: 1.10 ⇒ 1.13; Windows not updated yet.
--> DLC - Windows: 2.22 ⇒ 2.23; Mac: 1.10 ⇒ 1.13.
- LOST EMBER: 1.0.21 ⇒ 1.0.22.
- Overland: 747 ⇒ 751.
- Steel Division 2, and all its DLC: 32246 ⇒ 32246-fix-ranked.
- Soul Saga: 20.02.21.01 ⇒ 20.03.04.01.
- Warhammer 40,000: Mechanicus, and its DLC: 1.3.7.0 ⇒ 1.3.8.0; Linux was added to the game in Dec 2019, but not to the DLC.

Also, from updates/changelogs posted earlier:
- Commandos 2 - HD Remaster: 1.10.08 ⇒ 1.11.006.
- Cultist Simulator, and all its DLC - Windows: 2019.12.a.2.bis ⇒ 2019.11.a.1 (reversion, hence on par with Linux & Mac which were never updated).
- Heroes of Hammerwatch, and all its DLC: 103 ⇒ 104.
- Kenshi: 1.0.44 ⇒ 1.0.45c.
- Praetorians - HD Remaster: 1.02 ⇒ 1.03.
- RimWorld, and its DLC: 1.1.2561 rev846 ⇒ 1.1.2563 rev463.
- The Suicide of Rachel Foster: 1.0.3B ⇒ 1.0.3D.


@GOG, The Suicide of Rachel Foster has no game forum, and the forum link points to the General Discussion board; please add & fix.

RimWorld updated to 1.1.2564 (Steams latest 1.1.2565)

RimWorld has just received an update on GoG, which matches the one on Steam. There was no changelog posted for the GoG update, but there was one for Steam, which I'll post here.

Update 1.1.2564 released
This update contains balance changes and bugfixes.

If you're willing to help test, please join the testing Discord server: https://discord.gg/ryKTFr
Thanks!

Changes:

- Mech turret balance: Charge blaster turret cooldown 3.5->4.5 seconds. Inferno cannon turret cooldown 8.5->11.5 seconds Inferno cannon miss radius 3.5->3.9.
- Update player-created content: 172 names added.
- Languages updated.
- Ground-penetrating scanner rebalance. Random find time 4 work days->3 work days. Guaranteed find time 8 work days -> 6 work days.
- Ground-penetrating scanner now displays feedback about the current user's scanning speed, the random scan interval for this user, and the progress to a guaranteed find.
- Fixed a bug that could cause deep ores to generate outside the buildable area.
- Hunting decrees are now cancelled if there are not enough animals of the asked type left on the map.
- Monument markers, when canceled, can now be reinstalled again instead of disappearing.
- Mech clusters are now a lot less likely to fail finding position on difficult maps.
- Only inherited titles are now being removed from pawns after resurrection. So a resurrected pawn will keep his title if it wasn't inherited by someone else upon his death.
- Pawns with psychic harmonizers are now unaffected by others' harmonizers, to prevent runaway feedback loops.
- You can no longer lend colonists who are unfit for work.
- Removed errors from non-unique quest names
- Production decrees now only use more common stuff like wood, steel, and cloth, to reduce cases of near-impossible decrees.
- Add related quest gizmo to quest hives.
- Add "select hives" button to infestation kill quest so you can see which hives you need to kill.
- Fixed a bug that would cause insect kill quests to end only on killing every hive on the map (instead of every quest-spawned hive).
- Fixed a bug that would cause downed quest guards to never leave if they were injured during the quest and later healed.
- Fixed a bug that caused toxic spewers to affect caravans no matter where they are.
- Fixed a bug that made throne comfort not apply while reigning.
- Fixed a bug that could cause banished pawns to get stuck if they're on their way to a bed.
- Fixed pawn lend quest returning pawns to a random colony map instead of the map they were picked up from.
- If a nickname is empty in the character creation screen, the pawn's first name is used in the tooltips instead of an empty string.
- Fixed a bug that cause debug log spam after adding entropy link via dev tools and opening health tab.
- Optimized monument marker ticking to prevent performance loss with large monuments (checking for completion).