Let us open the thread with a summary of what we know so far:

GOG database (these games were detected a long time ago, they were probably scrapped for some reason):
Hummingwarp Interactive - Secret Little Haven
Sonalysts - Fleet Command, Sub Command, Dangerous Waters, 668(I) Hunter Killer ---> Also in Hidden GOG data
拾英工作室 - Tales of the Black Forest
Random Games Inc., MPS Labs - Wages of War (?)

Hidden GOG data (Galaxy API):
Receiver 2
Soulstice
Time Lock VR-1
Secrets of Grindea
Titanium Hound
Neptunia: Sisters VS Sisters
Shadow of the Guild
Dr. Chatelet Faith 神医
Monster Outbreak
Verge World

GOG logo on websites/trailers/official press releases:
The Lost Wild
Blight: Survival (Blight: No Man's Land)
Crisis in the Kremlin
Frozenheim
Kingdom of Night
Smurfs Kart
Saviorless
World of Anterra
Armed Fantasia
Penny Blood
Unreal Tournament 3 X
Akiba's Trip: Undead and Undressed Director's Cut
Medic: Pacific War
Stray Blade
Boom Blaster
Ova Magica
Tiny Life
Cloudscape
Athenian Rhapsody
Sang: The Desert Blade
Toasty Ashes of Dusk
Thief's Roulette
Hyper Team Recon
Elementallis
SteamDolls
Hero.EXE
Project Arrhythmia
Witchfall
The Girl From Arkanya
LAZR
Flame Keeper
Liam_99
Shattered: The Final Days
The Elephant Collection
Full Moon Rush
A Long Journey to an Uncertain End

Press sites:
SunnySide
Commandos 3 - HD Remaster
Circus Electrique
Floodland
EDENGATE: The Edge of Life
Slow Damage
Flame Keeper
Caverns of Mars: Recharged
AirportSim
Consortium Remastered
Everholm
Vengeance of Mr. Peppermint

Discord, Twitter, Forums, Kickstarter (The dev has already been in contact with GOG):
ANNO: Mutationem
Szrot
Forest Grove
Drova - Forsaken Kin
Sea Dogs: Legendary Edition
darkwebSTREAMER
Future Fragments
Westwood Shadows
Unfortunately Ninja
Chronicles of 2 Heroes
Zodiac Legion
Aerial_Knight’s Never Yield
Tears of Magic
CULTIC
The Grail
SP Grand Prix
Wanted: Dead
Girl Genius: Adventures In Castle Heterodyne
Cats and the Other Lives
illucid
Lords of Ravage
Streets of Rogue 2
Starcom: Unknown Space
Selaco
Demon Crush
Sword and Fairy 7
Hibernaculum
Toy Tactics
Agony: Lord of Hell
D.O.R.F. Real-Time Strategic Conflict
Moon Mystery
DROS
u4ia
Monolith

Discord, Twitter, Forums, Kickstarter (The dev would like to):
Instruments of Destruction
Islands of the Caliph
Dangerous Dave: Champion's Edition
Dying Breed
XEARZ
Spire of Sorcery
Supplice
Madshot
Dune: Spice Wars
Prehistoric Kingdom
Trial Out
Dark Quest: Board Game
Wizordum
Let Bions be Bygones
ERacer
Blossom Tales 2: The Minotaur Prince
NAIAD
Shattered Pixel Dungeon
Pixel Games UK
Flynt Buckler Wakes the Sleepy Castle
The Wayward Realms
Hollowbody
Compound Fracture
GrandMa Badass
Mandragora
Who's Lila?
Guns Undarkness
Open the Gates!
Darkenstein 3-D
The Phantom Fellows
Poly Bridge 2
Surviving the Humans
Foolish Mortals
DESORDRE
Earth of Oryn
Burnhouse Lane
Final Upgrade
Watch Over Christmas
RetroSpace
微光之镜 Glimmer in Mirror
The Spirit of the Samurai
Alterium Shift
Pitch Silent
Caves of Lore
Aquatico
Relentless Frontier
Glasshouse
Underspace
Sovereign Syndicate
Shadow Gambit: The Cursed Crew
Darkness Within
We Who Are About To Die
Shadows of Doubt
Gone rogue
Exekiller
Summer Daze: Tilly's Tale
Kona II: Brume
Roots of Yggdrasil
The Foretold: Westmark Legacy
Kerbal Space Program 2
Intruder in Antiquonia
!Ω Factorial Omega My Dystopian Robot Girlfriend
Workers & Resources: Soviet Republic
Frigato - Shadows of the Caribbean
Clover Days
Death Corp.
Hellscreen
Blood Nova
The Adventures of Bryan Scott
Gobliiins 5
Gravewood High
Scarlet Deer Inn
Galactix
DemonStar
Polars
Blood West

Legacy hidden GOG data (these games were detected a long time ago, they were probably scrapped for some reason):
Assassin's Creed 2
Assassin's Creed 3
Civilization V
Wages of War
Army Men: Air Tactics
Army Men: Sarge's Heroes
Army Men: Sarge's War
The Abbey
RAGE
Culpa Innata
Battle vs Chess
Lumberhill
HITMAN 2 Gold Edition
Dragon Throne
Seal of Evil
The Outforce
Poppy Playtime
Fleet Command
Sub Command
Dangerous Waters
688(I) HunterKiller
Bound By Love
FlatOut: Ultimate Carnage
FlatOut 3: Chaos & Destruction